Optical information recording medium and reproduction method

ABSTRACT

In a case where (i) a reflectance calculated from a reflected light amount obtained from a longest pit (P 1 max) or a longest space (S 1 max) in a first pit row is defined as a first reflectance and (ii) a reflectance calculated from a reflected light amount obtained from a longest pit (P 2 max) or a longest space (S 2 max) in the second pit row is defined as a second reflectance, the first pit row is formed such that the first reflectance becomes substantially identical with the second reflectance.

TECHNICAL FIELD

The present invention relates to (i) an optical information recordingmedium on which information can be recorded and (ii) a reproductionmethod and a reproduction device for reproducing the optical informationrecording medium.

BACKGROUND ART

In order to store a huge amount of information such as a high imagequality video, there has recently been a demand for increase incapacity, i.e., enhancement in recording density of optical informationrecording mediums. Under the circumstances, a super-resolution techniquehas been proposed in which an optical information recording medium(super-resolution medium), in which information is recorded with highdensity by a pit row that includes a pit whose length is shorter thanthat of an optical system resolution limit of a reproduction device, isreproduced at a reproduction light intensity (reproduction laser power)higher than that used to reproduce an optical information recordingmedium (normal medium) in which information is recorded by a pit rowthat does not include a pit whose length is equal to or shorter thanthat of the optical system resolution limit. Note that, in a case where(i) a wavelength of reproduction light to be emitted by the reproductiondevice is λ and (ii) a numerical aperture of an objective lens is NA,the optical system resolution limit is represented by λ/4 NA.

As an example of such a super-resolution medium, Patent Literature 1discloses an optical information recording medium having (i) a firstregion in which a content is recorded by pits (recesses and/orprojections) including a pit whose length is shorter than that of anoptical system resolution limit and (ii) a second region in which mediumidentification information for specifying a type of the medium isrecorded by pits. In this optical information recording medium, pitsthat represent the medium identification information each have a lengthequal to or longer than that of the optical system resolution limit.According to this arrangement, when the super-resolution medium isidentified, the super-resolution medium can be identified atreproduction laser power that is suitable for reproducing informationrecorded on a normal medium.

CITATION LIST Patent Literature

[Patent Literature 1]

International Publication No. 2007/100139 (Publication date: Sep. 7,2007)

SUMMARY OF INVENTION Technical Problem

However, in the optical information recording medium of PatentLiterature 1, the pits formed in the first region are different inlength and pit interval from the pits formed in the second region. Thatis, the first region differs from the second region in informationrecording density.

In such a case, there is a possibility that a difference occurs betweena reflectance obtained from the first region and a reflectance obtainedfrom the second region, and thus the reproduction device cannot assumethat these reflectances are substantially identical with each other. Ina case where (i) the above described difference in reflectance occursand (ii) reproduction of information in a first one of regions andreproduction of information in a second one of the regions aresequentially carried out, there may occur a phenomenon such as beingout-of-focus in the second one of the regions.

The present invention is accomplished in view of the above problem. Theobject of the present invention is to provide (i) an optical informationrecording medium that can improve information reproduction quality and(ii) a reproduction device and the like that can reproduce the opticalinformation recording medium.

Solution to Problem

In order to attain the object, an optical information recording mediumin accordance with an aspect of the present invention includes: arecording layer which includes (i) a first region in which informationis recorded by a first pit row that includes a pit whose length isshorter than that of an optical system resolution limit of areproduction device and (ii) a second region in which information isrecorded by a second pit row that is made up of pits whose length isequal to or longer than that of the optical system resolution limit, ina case where (i) a reflectance calculated from a reflected light amountobtained from a longest pit or a longest space in the first pit row isdefined as a first reflectance and (ii) a reflectance calculated from areflected light amount obtained from a longest pit or a longest space inthe second pit row is defined as a second reflectance, the first pit rowbeing formed such that the first reflectance becomes substantiallyidentical with the second reflectance.

Advantageous Effects of Invention

According to the aspect of the present invention, it is possible tobring about an effect of improving information reproduction quality.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view for explaining shapes of pits on a super-resolutionmedium in accordance with an embodiment of the present invention, where(a) illustrates an example of pit shapes in a data region and (b)illustrates a signal strength obtained from reproduction light which hasbeen emitted onto an area that (i) includes a longest space and (ii) isindicated by dashed dotted lines in (a) of FIG. 1.

FIG. 2 is a perspective view illustrating an appearance of thesuper-resolution medium.

FIG. 3 is a plan view illustrating a configuration of main parts of asubstrate included in the super-resolution medium.

FIG. 4 is a cross-sectional view illustrating a structure of thesuper-resolution medium.

FIG. 5 is a view illustrating a polarity of pits in the super-resolutionmedium.

FIG. 6 is a view illustrating an Example of the super-resolution medium,where (a) illustrates a state in which a medium information region ispartially (in the vicinity of a longest space) irradiated withreproduction light and (b) illustrates a state in which a data region ispartially (in the vicinity of a longest space) irradiated withreproduction light.

FIG. 7 is a perspective view illustrating an appearance of asuper-resolution medium that is a Comparative Example of thesuper-resolution medium of the present invention.

FIG. 8 is a plan view illustrating a configuration of main parts of asubstrate included in the super-resolution medium of the ComparativeExample.

FIG. 9 is a view illustrating a state in which a data region ispartially (in the vicinity of a longest space) irradiated withreproduction light L in the super-resolution medium of the ComparativeExample.

FIG. 10 is a view illustrating an experiment result of an ExperimentExample in relation to the super-resolution medium.

FIG. 11 is a view illustrating an experiment result of an ExperimentExample in relation to the super-resolution medium.

FIG. 12 is a view illustrating an Example of a super-resolution mediumin accordance with another embodiment of the present invention and aComparative Example of the super-resolution medium, where (a)illustrates a state in which a data region is partially (in the vicinityof a longest space) irradiated with reproduction light in the Exampleand (b) illustrates a state in which a data region is partially (in thevicinity of a longest space) irradiated with reproduction light L in theComparative Example.

FIG. 13 is a view illustrating an experiment result of an ExperimentExample in relation to the super-resolution medium.

FIG. 14 is a view illustrating a polarity of pits in a super-resolutionmedium in accordance with still another embodiment of the presentinvention.

FIG. 15 is a view illustrating an Example of the super-resolutionmedium, where (a) illustrates a state in which a medium informationregion is partially (in the vicinity of a longest space) irradiated withreproduction light and (b) illustrates a state in which a data region ispartially (in the vicinity of a longest space) irradiated withreproduction light.

FIG. 16 is a view illustrating, in an Example of a super-resolutionmedium in accordance with yet another embodiment of the presentinvention, a state in which a data region is partially (in the vicinityof a longest space) irradiated with reproduction light.

FIG. 17 is a block diagram illustrating an example of a reproductiondevice in accordance with still another embodiment of the presentinvention.

FIG. 18 is a block diagram schematically illustrating a configurationexample of a signal processing circuit/control section included in thereproduction device.

FIG. 19 is a view illustrating, in (a), a relation between a pit and anoutput signal in a case where a normal medium is sampled at areproduction clock suitable for the normal medium and is then decoded byPRML and, in (b), a relation between a pit and an output signal in acase where a normal medium is sampled at a reproduction clock suitablefor a super-resolution medium and is then decoded by PRML.

DESCRIPTION OF EMBODIMENTS Embodiment 1

The following description will discuss an optical information recordingmedium in accordance with an embodiment of the present invention withreference to FIGS. 1 through 11. In Embodiment 1, an optical informationrecording medium (hereinafter, referred to as “super-resolution medium1”) will be described as an example, and the super-resolution medium 1is a read-only medium and has a super-resolution region whose crosssectional structure is of a BD (Blu-ray Disc: Registered Trademark)type. Note, however, that Embodiment 1 is not limited to this. Thesuper-resolution medium 1 can be, for example, an optical informationrecording medium on which information can be recorded or a digitalversatile disc (DVD).

[Structure of Super-Resolution Medium 1]

FIG. 2 illustrates an appearance of the super-resolution medium 1 inaccordance with Embodiment 1. As illustrated in FIG. 2, thesuper-resolution medium 1 which is a discoid medium includes a recordinglayer having, in advance, (i) a data region 2 (first region) in which,for example, a content such as a video or software is recorded and (ii)a medium information region 3 (second region) in which, for example,information relating to the super-resolution medium 1 is recorded.

FIG. 3 is an enlarged view of part a of the super-resolution medium 1illustrated in FIG. 2. As illustrated in FIG. 3, in the data region 2and the medium information region 3, a plurality of pits P1 (pits infirst pit row), a plurality of pits P2 (pits in second pit row), aplurality of spaces S1 (first space) formed between the plurality ofpits P1, and a plurality of spaces S2 (second space) formed between theplurality of pits P2 are formed so as to make rows which (i) extend in acircumferential direction and (ii) are apart from each other atpredetermined track pitches TpD and TpR (predetermined intervals). Inother words, a first pit row is formed by pits P1 and spaces S1 in thedata region 2, and a second pit row is formed by pits P2 and spaces S2in the medium information region 3.

As a method for recording information in the data region 2 and themedium information region 3, a mark-edge recording method is employed inwhich information can be recorded by the use of (i) pits P1 and P2 whichare different in shape and size and (ii) spaces S1 and S2 which aredifferent in shape and size. In Embodiment 1, among such methods, amodulation recording method (record encoding method) called 1-7 PP (1-7Parity Preserve/Prohibit RMTR (Repeated Minimum Transition Run Length))is employed. That is, in this method, the pits P1 and P2 are formed witha modulation method which is one of (1,7) RLL (Run Length Limited)modulations. For example, on a BD, information is recorded by pits (orrecording mark) of 2T to 8T and spaces of 2T to 8T. In Embodiment 1, forconvenience, a length of a pit P1 in the data region 2 is sometimesrepresented by “D2T to D8T”, and a length of a pit P1 in the mediuminformation region 3 is sometimes represented by “R2T to R8T”.

Note that, in the modulation, (i) a bit string pattern of originalinformation is converted into a recording pattern which has apredetermined frequency bandwidth (that is, has a combination ofrecording marks and spaces which are restricted to some types), withoutdepending on the bit string pattern of the original information (i.e.,information before modulation) and (ii) a length of a shortest recordingmark or space is enlarged so as to be longer than its length in theoriginal information, and thus recording density is magnified. In a caseof the 1-7 PP modulation recording method, a 2-bit unit in originalinformation is converted into a 3-channel-bit unit so that recordingmarks and spaces are obtained which have restricted lengths of 2-channelbit (2T) to 8-channel bit (8T) as a modulated recording pattern, andthus a frequency bandwidth is restricted. Further, a length of ashortest recording mark and a length of a shortest space are enlarged by1.5 times from those in the original information. Therefore, themodulation carried out with the 1-7 PP modulation recording method issuitable for high density recording. Note that the modulation method isnot limited to the 1-7 PP modulation and other modulation methodssuitable for high density recording can be employed. Examples of suchmodulation methods encompass (1,7) RLL modulation other than the 1-7 PPmodulation, 8/16 modulation, and (2,7) RLL modulation.

(Data Region 2)

As illustrated in FIG. 2, the data region 2 is provided between mediuminformation regions 3, and the content is recorded in the data region 2by providing the pits P1 when the substrate is formed. The pits P1 havelengths of D2T to D8T as illustrated in FIG. 3 and a length D2T of ashortest pit P1min is shorter than an optical system resolution limit ofa reproduction device. That is, the content is recorded by pits P1 whichinclude the pit P1 whose length is shorter than the optical systemresolution limit of the reproduction device (i.e., super-resolutionrecording form), and this makes it possible to record information withhigher density than that of a normal medium.

Note that a pit having the length of D8T is a longest pit P1max amongthe plurality of pits P1 formed in the data region 2. Moreover, amongthe plurality of spaces S1 formed between the plurality of pits P1, ashortest one of the spaces S1 is a shortest space S1min (notillustrated) and a longest one of the spaces S1 is a longest space S1max(longest first space) (see (a) of FIG. 1).

(Medium Information Region 3)

As illustrated in FIG. 2, the medium information region 3 is provided inadvance in each of an innermost peripheral part and an outermostperipheral part of the super-resolution medium 1, and informationrelating to the super-resolution medium 1 is recorded in the mediuminformation region 3 by the pits P2 (normal recording form). The pits P2have lengths of R2T to R8T as illustrated in FIG. 3, and a length R2T ofa shortest pit P2min is equal to or longer than the optical systemresolution limit of the reproduction device. That is, lengths of all thepits P2 in the medium information region 3 are longer than the shortestpit P1min in the data region 2, and information recording density in themedium information region 3 is lower than that in the data region 2.

Note that a pit having the length of R8T is a longest pit P2max amongthe plurality of pits P2 formed in the medium information region 3.Moreover, among the plurality of spaces S2 formed between the pluralityof pits P2, a shortest one of the spaces S2 is a shortest space S2min(not illustrated), and a longest one of the spaces S2 is a longest spaceS2max (longest second space) (see (a) of FIG. 6).

The medium information region 3 is provided in each of the innerperiphery and the outer periphery of the super-resolution medium 1.Note, however, that the medium information region 3 is not limited tothis and can be provided in any one of the inner periphery and the outerperiphery.

As above described, the super-resolution medium 1 is an opticalinformation recording medium in which a so-called super-resolutiontechnique is used. Moreover, the data region 2 is a super-resolutionregion from which information is reproduced by the super-resolutiontechnique, and the medium information region 3 is a non-super-resolutionregion from which information is reproduced without using thesuper-resolution technique.

(Example of Information Recorded in Medium Information Region 3)

The information relating to the super-resolution medium 1 encompasses,for example, medium identification information for specifying thesuper-resolution medium 1, region location information for specifying alocation in the data region 2, and data management information formanaging data recorded in the data region 2 and in the mediuminformation region 3.

The medium identification information encompasses, for example, (i) disktype identification information such as information indicative of a type(BD, DVD, etc., or read-only, write-once, rewritable, etc.) and astorage capacity of the optical information recording medium and/or (ii)individual identification information (such as unique number of mediumfor copy protection) for identifying an individual optical informationrecording medium (i.e., identifying the super-resolution medium 1).

It is preferable that the information relating to the super-resolutionmedium 1 includes reproduction speed information, reproduction lightintensity information, polarity information, and/or region locationinformation. The medium identification information can includereproduction speed information and reproduction light intensityinformation.

The reproduction speed information is indicative of a reproduction speedrequired for seamlessly reproducing a content such as video information.Moreover, the reproduction speed information includes (i) reproductionspeed range information which is necessary to obtain an analog waveformthat can be converted into a digital signal in a case where thesuper-resolution medium 1 is irradiated with appropriate reproductionlight (reproduction laser), (ii) digital process information which isnecessary to convert an analog waveform, which has been reproduced toreproduce a content or the like, into a digital signal, or (iii) acombination of these pieces of information.

The reproduction speed range information is information defining areproduction speed for stably obtaining an analog waveform bysuper-resolution reproduction. Specifically, the reproduction speedrange information is necessary because, in a case where super-resolutionreproduction is enabled by heat, (i) an excessively high reproductionspeed causes insufficient heat and accordingly the super-resolutionreproduction cannot be carried out and (ii) an excessively lowreproduction speed causes excessive increase in generated heat energyand accordingly the medium is damaged.

Note that the reproduction speed indicates a linear speed inreproduction (i.e., a relative velocity which (i) is between a locationof an optical head (from which reproduction light is emitted) and areproduction location of the optical information recording medium and(ii) is caused when the optical information recording medium is rotatedby a spindle motor in reproduction of the medium).

The digital process information includes, for example, reproductionclock switching information, reproduction speed switching information,or a combination of these pieces of information. These pieces ofinformation are necessary, for example, for converting, into a digitalsignal, an analog waveform which has been obtained in a case whereinformation is reproduced which has been recorded with the 1-7 PPmodulation method in the data region 2 and the medium information region3 which are different in recording density.

The reproduction light intensity information includes reproduction lightintensity range information which is necessary for obtaining, in a casewhere the super-resolution medium 1 is irradiated with reproductionlight (reproduction laser), an analog waveform that can be convertedinto a digital signal. In a case where super-resolution reproduction isenabled by heat, (i) an excessively low reproduction light intensitycauses insufficient heat and accordingly the super-resolutionreproduction cannot be carried out and (ii) an excessively highreproduction light intensity causes excessive increase in generated heatenergy and accordingly the medium is damaged and a load is applied tothe reproduction device. The reproduction light intensity rangeinformation is information which defines reproduction light intensityfor obtaining a stable analog waveform without applying an excessiveload to the reproduction device by super-resolution reproduction.

The polarity information includes information such as pit polarityinformation indicative of whether the pits P1 and P2 are concave (in-pitform) or convex (on-pit form) with respect to a side from whichreproduction light for the super-resolution medium 1 is emitted. Forexample, in a case where a tracking servo is operated with a push-pull(PP) method or a differential push-pull (DPP) method, a polarity (i.e.,positive or negative) of a tracking error signal varies depending on apolarity of the pits P1 and P2. The pit polarity information makes itpossible to immediately determine whether a tracking error signal, whichis in a state (on-track state) where an irradiation location ofreproduction light is at a center of a track, is (i) at a center ofamplitude of a tracking error signal whose first derivation valuerelating to a distance from a center of the super-resolution medium 1 ispositive or (ii) at a center of amplitude of a tracking error signalwhose first derivation value relating to the distance from the center ofthe super-resolution medium 1 is negative.

The region location information includes, for example, data regionlocation information indicative of a location of the data region 2 inthe super-resolution medium 1. The data region location information canbe, for example, (i) information indicative of starting location and/orending location of reproduction of information in the data region 2,(ii) information indicative of starting location and/or ending locationof reproduction of information in the medium information region 3, or(iii) a combination of these pieces of information. The data regionlocation information is used, for example, in a case where thereproduction device sequentially reproduces pieces of information in thedata region 2 and the medium information region 3 which are different inrecording density and for which suitable information reproductionconditions are differently set. Specifically, the data region locationinformation is necessary for the reproduction device to switch one ofthe information reproduction conditions, which are set for respective ofthe data region 2 and the medium information region 3, to the other.

Note that the information reproduction condition indicates (i) any ofconditions such as reproduction light intensity, a reproduction speed,and a type of tracking servo and (ii) a condition that needs to be setfor the reproduction device to reproduce information recorded in theoptical information recording medium.

(Specific Structure of Super-Resolution Medium 1)

The following description will discuss a specific structure of thesuper-resolution medium 1. FIG. 4 is a cross-sectional view of thesuper-resolution medium 1. FIG. 5 illustrates a polarity of the pits P1and P2.

As illustrated in FIG. 4, the super-resolution medium 1 includes a coverlayer 6, a functional layer 5, and a substrate 4 which are arranged inthis order from a side which is irradiated with reproduction light Lemitted by the reproduction device.

The substrate 4 is, for example, made of polycarbonate (PC) and has adiameter of approximately 120 mm and a thickness of approximately 1.1mm. On the side to which the reproduction light L is emitted, pieces ofinformation are recorded in concave pits P1 and P2 formed in thesubstrate 4 (in-pit form) (see FIG. 5). That is, recessed parts formedin the substrate 4 are the pits P1 and P2. Note that the pits P1 and P2can be (i) convex pits or (ii) concave pits and convex pits. That is,the pits P1 and P2 can be concave and/or convex. Note that a structurein which the pits P1 and P2 are convex pits (on-pit form) will bedescribed in Embodiment 3.

The cover layer 6 is, for example, made of ultraviolet-curable resin andhas a thickness of approximately 100 μm (for example, has a refractiveindex of 1.50 with respect to reproduction light L having a wavelengthλ=405 nm). The cover layer 6 merely needs to be made of a materialhaving high transmittance with respect to the wavelength of thereproduction light L and can be, for example, formed from (i) a filmmade of polycarbonate (polycarbonate film) and (ii) a transparentadhesive material.

The functional layer 5 is a layer for generating a super-resolutionphenomenon and is formed on the substrate 4 by, for example, sputtering.The functional layer 5 is, for example, made of tantalum (Ta) and has athickness of approximately 12 nm. The functional layer 5 can be made upof two or more types of films. In this case, for example, the functionallayer 5 can be made up of (i) a light absorption film which can absorbthe reproduction light L, has a thickness of approximately 8 nm, and ismade of tantalum and (ii) a super-resolution reproduction film which hasa thickness of approximately 50 nm and is made of zinc oxide (ZnO). Inthis case, it is possible to increase information recording density.

It is possible to provide two or more functional layers 5. In this case,an intermediate layer(s) can be provided between the two or morefunctional layers 5. The intermediate layer can be made of, for example,ultraviolet-curable resin. However, a material of the intermediate layeris not limited to this, provided that the material has hightransmittance with respect to the wavelength of the reproduction lightL. Each of the intermediate layer(s) can be provided with at least pitsP1 on the side to which the reproduction light L is emitted. In thiscase, it is possible to further increase a storage capacity of thesuper-resolution medium 1.

By providing the functional layer 5 above described, informationrecorded by the pits P1 in the data region 2 can be reproduced. In acase where the functional layer 5 is made up of a thin metal film or thelike, it is possible to reproduce a signal of a pit, whose length isshorter than that of an optical system resolution limit, by changing atemperature of the functional layer 5. Alternatively, in a case wherethe functional layer 5 is made up of a light absorption film and asuper-resolution reproduction film and the pits P1 are irradiated withthe reproduction light, an irradiation region (laser spot) of thereproduction light is formed on the super-resolution medium 1, anddistribution of transmittance is caused, in the irradiation region, bytemperature distribution that is caused due to light intensitydistribution. As a result, the irradiation region goes into apseudo-shrinkage state, and thus information recorded by the pits P1 canbe reproduced. From this, it is possible to record information more thanthat recorded in a normal medium.

(Pit Shape in Each Region)

The following description will discuss a shape (size) of pits P1 in thesuper-resolution medium 1 with reference to FIG. 1. (a) of FIG. 1illustrates an example of shapes of pits in the data region 2, and (b)of FIG. 1 illustrates a signal strength obtained by irradiating, withreproduction light L, an area which includes a longest space S1max andis indicated by dashed dotted lines in (a) of FIG. 1. In Embodiment 1, aratio between (i) a length of a pit (recording mark) and (ii) a lengthof a space (e.g., space of 8T) corresponding to the pit (e.g., pit of8T) is referred to as “duty”, and a case where the ratio is 1:1 isreferred to as “duty of 50%”.

The lengths (duty) of the pit and the space can be increased ordecreased within a range in which information can be reproduced by thereproduction device. The inventors of the present invention focused onthe fact that the lengths (duty) can be increased or decreased, andfound that it is possible to improve, in a super-resolution mediumhaving a super-resolution region and a non-super-resolution region, areflectance of the super-resolution region by changing lengths of pitsand spaces, and it is accordingly possible to improve informationreproduction quality in the super-resolution medium.

In order to improve the reproduction quality, in the super-resolutionmedium 1, the pits P1 are formed in the data region 2 such that areflectance (first reflectance) in the data region 2 becomessubstantially identical with a reflectance (second reflectance) in themedium information region 3. In other words, a first pit row whichincludes the pits P1 and is formed in the data region 2 is formed suchthat the first reflectance becomes substantially identical with thesecond reflectance. In still other words, the pits P1 are formed in thedata region 2 such that the reproduction device can deal with the firstand second reflectances as substantially identical reflectances, withoutproviding different definitions of reflectance in respective of the dataregion 2 and the medium information region 3 with respect to thesuper-resolution medium 1 or the reproduction device.

Note that, in Embodiment 1, the reflectance is a ratio between (i) avalue calculated from a maximum reflected light amount from a recordinglayer and (ii) intensity of reproduction light emitted, for example, bythe reproduction device. Here, the maximum reflected light amount ismeasured by a detector of the reproduction device when a longest pit ora longest space is irradiated with the reproduction light while trackinga recording track (track). Note that the reflectance is not limited tothe above described ratio but can be, for example, a ratio betweenintensity of reproduction light and intensity of light reflected fromthe recording layer.

That is, in the super-resolution medium 1 of Embodiment 1, the firstreflectance (i.e., a reflectance obtained from the data region 2) is areflectance calculated from a reflected light amount obtained from thelongest pit P1max or the longest space S1max in the first pit row.Meanwhile, the second reflectance (i.e., a reflectance obtained from themedium information region 3) is a reflectance calculated from areflected light amount obtained from the longest pit P2max or thelongest space S2max in the second pit row. Note that the reflected lightamount obtained from the longest pit or the longest space can be said asan amount of reflected light caused when the reproduction light L isreflected from the longest pit or the longest space.

Here, the recording layer is a layer which is of a normal medium or asuper-resolution medium and in which information is recorded. In a caseof a read-only optical information recording medium, the recording layerincludes pits and a reflecting layer. The reflecting layer is a layerwhich is provided between a cover layer and a substrate that makes itpossible to reproduce information recorded on the normal medium or thesuper-resolution medium. In the super-resolution medium, the reflectinglayer is a functional layer. In the normal medium, the reflecting layeris, for example, made of metal or a metal alloy and has a thickness ofseveral tens of nanometers.

More specifically, as illustrated in (a) of FIG. 1, pits P1 (each ofwhich has an elliptical shape indicated by solid lines in (a) of FIG. 1)in the super-resolution medium 1 are one size smaller than pits P1′(each of which has an elliptical shape indicated by dotted lines in (a)of FIG. 1) in a general super-resolution medium. That is, the pits P1are formed so that a duty of the pits P1 becomes smaller than a duty ofthe spaces S1 (i.e., becomes smaller than a duty of the pits P1′ in thegeneral super-resolution medium). Note that an example of the generalsuper-resolution medium encompasses a super-resolution medium inComparative Example illustrated in FIG. 9. In this case, the pits P1′correspond to pits P101 shown in FIG. 9.

In Embodiment 1, the pit P1 in the super-resolution medium 1 and the pitP1′ in the general super-resolution medium are similar figures. That is,a length of the pit P1 in a radial direction is changed in accordancewith change in duty, as with a length in the circumferential direction.For example, in a case where a duty is 50%, a length of a pit (pit P1′)is 0.448 μm, and a width of the pit (pit P1′) is 0.112 μm, a length ofthe pit (pit P1) becomes 0.404 μm and a width of the pit (pit P1)becomes 0.101 μm when the duty has been changed to 45%. Note, however,that it is sufficient to change at least the length in thecircumferential direction, and the width can be identical with, forexample, the length of the pit P1′.

Here, as above described, in the super-resolution medium 1, the dataregion 2 is a super-resolution region in which information is recordedwith the plurality of pits P1 whose length is shorter than that of theoptical system resolution limit, and the medium information region 3 isa non-super-resolution region in which information is recorded with theplurality of pits P2 whose length is equal to or longer than that of theoptical system resolution limit.

In general, upper limits of a pit length and a space length (i.e., pitinterval) are defined depending on a modulation recording method that isused to record information. Therefore, depending on a length of ashortest pit, information recording density in an optical informationrecording medium varies. In a case of the above described 1-7 PPmodulation recording method, a shortest pit length is 2T, and a longestpit length is 8T which is four times longer than the shortest pitlength.

That is, in the super-resolution medium 1, the pit P1 have the lengthdifferent from that of the pit P2, and therefore the data region 2 isdifferent from the medium information region 3 in the informationrecording density. In this case, if the length of the pit P1 isidentical with that of the space S1 and the length of the pit P2 isidentical with that of the space S2 (i.e., duty of 50%), there is apossibility that a difference occurs between a reflectance at apredetermined location in the data region 2 and a reflectance at apredetermined location in the medium information region 3, and thus thereproduction device cannot assume that these reflectances obtained bythe reproduction device are identical with each other. Note that thepredetermined locations are locations corresponding to each otherbetween the data region 2 and the medium information region 3. Forexample, the predetermined locations are respective longest pits (i.e.,longest pits P1max and P2max) or respective longest spaces (i.e.,longest spaces S1max and S2max) in the data region 2 and the mediuminformation region 3.

Moreover, in general, various controls such as focus control are carriedout in a reproduction device with the use of a reflectance. Therefore,in a case where the above described difference in reflectance occurs andreproduction of information in a first one of regions (e.g., the dataregion 2) and reproduction of information in a second one of the regions(e.g., the medium information region 3) are sequentially carried out,for example, a size of an irradiation region formed by reproductionlight on an optical information recording medium in the second one ofthe regions changes (i.e., out of focus), and the reproduction devicemay need to carry out the focus control again every time the regions areswitched.

In the super-resolution medium 1, although there is a difference inrecording density between the data region 2 and the medium informationregion 3, the pits P1 having a shape (i.e., the shape is specified)which is different from that of the pits P1′ in the generalsuper-resolution medium are formed in the data region 2 (see (a) of FIG.1). Therefore, even though there is the difference in recording density,it is possible to cause the reproduction device to deal with thesuper-resolution medium 1 as a medium in which the reflectance obtainedfrom the data region 2 is identical with the reflectance obtained fromthe medium information region 3. The following description will discussthe reason that these two reflectances are substantially identical witheach other, with reference to (b) of FIG. 1.

(b) of FIG. 1 shows a difference in signal strength between thesuper-resolution medium 1 and the general super-resolution medium causedin a case where the longest space S1max in the data region 2 illustratedin (a) of FIG. 1 is irradiated with reproduction light L. In (b) of FIG.1, signal strength is indicated with is in a range from a location x1 toa location x2 in the circumferential direction in (a) of FIG. 1.Moreover, in (b) of FIG. 1, “T” represents a maximum value of the signalstrength obtained when a non-super-resolution region (e.g., the mediuminformation region 3) is irradiated with the reproduction light L and“T₀” represents signal strength of zero. A value proportional to a valueobtained by T−T₀ is measured as a reflectance.

As illustrated in (b) of FIG. 1, a maximum value of signal strength(indicated by a dotted line in (b) of FIG. 1) obtained from the generalsuper-resolution medium is lower than T. On the other hand, in a case ofthe super-resolution medium 1 (indicated by a solid line in (b) of FIG.1), a maximum value of signal strength is substantially identical withT. That is, the reflectance obtained from the super-resolution medium 1is higher than the reflectance obtained from the generalsuper-resolution medium and is substantially identical with thereflectance obtained from the non-super-resolution region.

In a case where a space of the general super-resolution medium isirradiated with the reproduction light L as illustrated in (a) of FIG.1, not only the space but also the pits P1′ are irradiated with thereproduction light L. In general, signal strength obtained from a pit islower than signal strength obtained from a space, and therefore thesignal strength becomes lower in proportion to an amount of reproductionlight with which the pit P1′ is irradiated.

On the other hand, in the super-resolution medium 1, the duty isadjusted and the pits P1 are formed such that a length of a pit P1becomes smaller than a length of a space S1 which corresponds to the pitP1, as above described. That is, as illustrated in (a) of FIG. 1, thepits P1 are formed in the data region 2 such that the length of thelongest space S1max becomes equal to or longer than a diameter of theirradiation region (indicated by a circle in (a) of FIG. 1) formed bythe reproduction light L on the super-resolution medium 1.

With the arrangement, the pits P1 are not (or are hardly) irradiatedwith the reproduction light L with which the longest space S1max isirradiated, and it is therefore possible to mostly eliminate apossibility that signal strength becomes lower. From this, it ispossible to obtain signal strength (i.e., reflectance) that issubstantially identical with that obtained from the medium informationregion 3 (longest space S2max) which is the non-super-resolution region.

As above described, in the super-resolution medium 1, each of the pitsP1 has the shape (size) as above described. It is therefore possible toreduce a possibility that is caused because reflectances obtained fromrespective regions, from which pieces of information are sequentiallyreproduced (i.e., during sequential reproduction across the regions),are not substantially identical with each other (i.e., a differenceoccurs between reflectances to a degree that the reproduction devicecannot deal with the reflectances as identical reflectances). Forexample, it is possible to reduce a possibility that a size of anirradiation region changes which is formed by reproduction light on anoptical information recording medium. Therefore, even during thesequential reproduction, it is possible to promptly and surely reproduceinformation without repeatedly carrying out focus control.

That is, during the sequential reproduction, it is possible to reproduceinformation from a second one of regions without repeatedly carrying outa control that (i) is included in reproduction controls for a first oneof the regions and (ii) can be maintained in the second one of theregions. This makes it possible to improve information reproductionquality.

In the 1-7 PP modulation recording method, an amount of reflected light(reflected light amount) obtained when the optical information recordingmedium is irradiated with reproduction light is determined mainly basedon a length of a longest space, although pits in an adjacent trackslightly influence the reflected light amount. Moreover, a reflectanceis increased in accordance with an increase in reflected light amount.

In view of this, in the super-resolution medium 1, the pits P1 areformed in the data region 2 such that the length of the longest spaceS1max becomes equal to or longer than the diameter of the irradiationregion as above described, and thus the reflectance in the longest spaceS1max is enhanced. That is, the pits P1 are formed in the data region 2such that the reflectance in the longest space S1max becomessubstantially identical with the reflectance in the longest space S2max(see (a) of FIG. 6).

Note that the length of the longest space S1max does not necessarilyneed to be equal to or larger than the diameter of the spot formed bythe reproduction light L. That is, the length of the longest space S1maxcan be shorter than the diameter, provided that the reflectance obtainedfrom the data region 2 is substantially identical with the reflectanceobtained from the medium information region 3 (for example, providedthat the reproduction device can assume that the reflectance obtainedfrom the data region 2 (longest space S1max) is identical with thereflectance obtained from the medium information region 3 (longest spaceS2max)). An example of this case will be described in Embodiment 2.

In a case where another modulation recording method is employed, it isnot necessary to set the shapes (duty) of the pits P1 while using, as acriterion, the reflectance obtained from the longest space S1max inorder to improve the reflectance in the data region 2. For example, itis possible to set the shapes of the pits P1 while using, as acriterion, the reflectance obtained from the longest pit P1max.

The pits P1 and the pits P2 provided in the substrate 4 of thesuper-resolution medium 1 are formed by, for example, carrying outinjection molding with respect to a master disk which has been preparedby a cutting machine. Note, however, that, in order to prevent anincrease in time required for preparing the master disk, it ispreferable that the pits P1 and the pits P2 are sequentially formed.However, the length of the pit P1 is different from not only the lengthof the pit P2 but also the length of the pit P1′. Therefore, asconditions for forming the pits P1 and the pits P2, not only speeds forforming the pits P1 and the pits P2 but also write strategies aredifferent between the data region 2 and the medium information region 3.From this, pits P1 and pits P2 in the vicinity of a boundary between thedata region 2 and the medium information region 3 are to haveintermediate shapes between a shape of the pit P1 and a shape of the pitP2, and this may cause a case where information cannot be properlyreproduced. Under the circumstances, it is preferable to provide anintermediate region which is an intended range from the boundary betweenthe data region 2 and the medium information region 3. In this case, inthe intermediate region, predetermined information, which does notinfluence reproduction of information relating to the super-resolutionmedium 1 and information such as a content, can be recorded by pits P1and/or pits P2.

Example

Next, the following description will discuss an Example of thesuper-resolution medium 1 of Embodiment 1, with reference to FIG. 6.FIG. 6 is a view illustrating an Example of the super-resolution medium1, where (a) illustrates a state in which the medium information region3 is partially (in the vicinity of the longest space S2max) irradiatedwith the reproduction light L and (b) illustrates a state in which thedata region 2 is partially (in the vicinity of the longest space S1max)irradiated with the reproduction light L.

In this Example, the super-resolution medium 1 has the above describedsize and includes the layers whose thickness and material have beendescribed above. A track pitch TpR of the medium information region 3and a track pitch TpD of the data region 2 are 0.32 μm. Note that thetrack pitch TpR of the medium information region 3 can be 0.35 μm.Moreover, in this Example, information is recorded with the use of the1-7 PP modulation recording method.

As illustrated in (a) of FIG. 6, in the medium information region 3, thelongest pit P2max (pit of 8T) and the longest space S2max (space of 8T)have a length of 0.596 μm. That is, the duty of the pits P2 and the dutyof the spaces S2 are both 50%, and the shortest pit P2min (pit of 2T,not illustrated) in the medium information region 3 has the length of0.149 μm.

On the other hand, as illustrated in (b) of FIG. 6, in the data region2, the longest pit P1max (pit of 8T) has a length of 0.404 μm and thelongest space S1max (space of 8T) has a length of 0.492 μm. That is, theduty of the pits P1 is approximately 45% and the duty of the spaces S1is approximately 55%, and the shortest pit P1min (pit of 2T, notillustrated) in the data region 2 has a length of 0.101 μm (≈0.112μm×2×0.45).

Note that the length of 0.112 μm is a length of a shortest pit P101minin a data region 102 in Comparative Example which will be describedlater. That is, the data region 2 in this Example is obtained bychanging the duty in the data region 102 of Comparative Example as abovedescribed.

The medium information region 3 has a storage capacity of 25 GB, and thedata region 2 has a storage capacity of 33.3 GB (these storagecapacities correspond to storage capacities which are obtained in a casewhere the super-resolution medium 1 is a disk having a diameter of 120mm).

In a case where a wavelength of reproduction light L (i.e., reproductionlight L of a reproduction optical system) that is emitted by thereproduction device which can reproduce the super-resolution medium 1 ofExample 1 is λ and a numerical aperture of an objective lens included inthe reproduction device is NA, the optical system resolution limit ofthe reproduction device is represented by λ/4 NA. In Example 1, λ=405 nmand NA=0.85, and the optical system resolution limit is λ/4 NA=0.119 μm(=119 nm).

That is, in the super-resolution medium 1 of Example 1, the data region2 is a super-resolution region in which at least one pit P1 (space S1)has a length that is shorter than that of the optical system resolutionlimit (i.e., shorter than 119 nm). Meanwhile, the medium informationregion 3 is a non-super-resolution region in which all the pits P2(spaces S2) have lengths which are equal to or longer than that of theoptical system resolution limit (i.e., equal to or longer than 119 nm).In other words, the super-resolution medium 1 of Example 1 has therecording layer including (i) the data region 2 in which information isrecorded by a first pit row including a pit P1 whose length is shorterthan 119 nm and (ii) the medium information region 3 in whichinformation is recorded by a second pit row made up of pits each ofwhich has a length of equal to or longer than 119 nm. Thesuper-resolution medium 1 is reproduced by the reproduction device inwhich the wavelength λ of the reproduction light and the numericalaperture NA of the objective lens are as above described.

Comparative Example

The following description will discuss a super-resolution medium 101 asComparative Example of Embodiment 1, with reference to FIGS. 7 through9. FIG. 7 illustrates an appearance of the super-resolution medium 101,and FIG. 8 is an enlarged view of a part b of the super-resolutionmedium 101. FIG. 9 illustrates a state in which a data region 102 ispartially (in the vicinity of a longest space S101max) irradiated withreproduction light L. Note that a reproduction device for reproducingthe super-resolution medium 101 is the one which is used in Example 1.

The super-resolution medium 101 has a fundamental structure which issimilar to that of the super-resolution medium 1, except that shapes ofpits P101 (spaces S101) in the data region 102 are different from thoseof the pits P1 (spaces S1) in the data region 2. That is, shapes and anarrangement of pits P102 in the medium information region 103 areidentical with shapes and the arrangement of the pits P2 illustrated in(a) of FIG. 6, and “R2T” and “R8T” in FIG. 8 correspond to “R2T” and“R8T”, respectively.

Specifically, as illustrated in FIG. 7, the super-resolution medium 101includes in advance (i) the data region 102 in which a content isrecorded and (ii) the medium information region 103 in which informationrelating to the super-resolution medium 101 is recorded, as with thesuper-resolution medium 1. Moreover, as illustrated in FIG. 8, theplurality of pits P101 and the plurality of spaces S102 provided betweenthe plurality of pits P101 are formed in the data region 102 so as to bearranged in rows in a circumferential direction at a predetermined trackpitch, and the plurality of pits P102 and the plurality of spaces S102provided between the plurality of pits P102 are formed in the mediuminformation region 103 so as to be arranged in rows in thecircumferential direction at a predetermined track pitch.

In the data region 102, a shortest pit P101min (pit of 2T, notillustrated) has a length D2T′ of 0.112 μm and, as illustrated in FIG.9, a longest pit P101max (pit of 8T) has a length D8T′ of 0.448 μm.Moreover, a longest space S101max (space of 8T) also has a length of0.448 μm. That is, in this Comparative Example, a duty of the pits P101and a duty of the spaces S101 are both 50%. Note that the data region 2has a storage capacity of 33.3 GB (which corresponds to a storagecapacity obtained in a case where the super-resolution medium 101 is adisk having a diameter of 120 mm).

[Comparison with Comparative Example]

In the super-resolution medium 101 of Comparative Example, not only thespaces S101 but also the pits P101 are partially irradiated with thereproduction light L as illustrated in FIG. 9. That is, a reflectanceobtained by the reproduction device is decreased by a degree thatcorresponds to an amount of the reproduction light L with which the pitsP101 are irradiated. From this, the reflectance is lower than areflectance that is obtained from the longest space S102max (notillustrated) in the medium information region 103, and it thereforebecomes necessary to repeatedly carry out focus control during thesequential reproduction, depending on circumstances.

On the other hand, in the super-resolution medium 1 of the abovedescribed Example, the duties (i.e., the length of the pit P1 and thelength of the space S1) in the data region 2 are as described above.That is, the duty of the pits P1 in the data region 2 is smaller thanthe duty of the pits P101 in the data region 102 and, as illustrated in(b) of FIG. 6, the length of the longest space S1max is longer than theirradiation region formed by the reproduction light L.

As such, in the super-resolution medium 1, the pits P1 present aroundthe longest space S1max are not irradiated with the reproduction lightL, and therefore the reproduction device can deal with the reflectanceobtained from the longest space S1max in the data region 2 as beingidentical with the reflectance obtained from the longest space S2max inthe medium information region 3. Therefore, according to thesuper-resolution medium 1, it is possible to promptly and surelyreproduce, during the sequential reproduction, pieces of informationwhich are recorded in separate regions.

Experiment Example

Next, the following description will discuss an Experiment Examplerelating to the super-resolution medium 1 of Embodiment 1, withreference to FIG. 10 and FIG. 11. FIGS. 10 and 11 illustrate results ofexperiments carried out in the Experiment Example relating to thesuper-resolution medium 1. In this Experiment Example, appropriatelengths (duty) of the pits P1 and the spaces S1 in the data region 2 areverified. Note, however, that the results of verification are merely anexample, and a tolerance thereof can be changed in accordance with areproduction status.

FIG. 10 shows results of measuring reflectances obtained from opticalinformation recording mediums “Pit group A” through “Pit group D” whichare different in pit length. The measurement is carried out with a BDstandard evaluation device (ODU-1000 (λ: 405 nm, NA: 0.85) manufacturedby PULSTEC INDUSTRIAL CO., LTD.), and a reproduction light intensity is1.0 mW in the measurement.

In FIG. 10, “Pit group A” is an optical information recording mediumincluding a non-super-resolution region which is made up of only pitswhose lengths are equal to or longer than that of an optical systemresolution limit. A shortest pit in “Pit group A” has a length of 0.149μm (with the duty of 50%).

Each of “Pit group B” through “Pit group D” is an optical informationrecording medium which includes a super-resolution region having atleast one pit whose length is shorter than that of the optical systemresolution limit. A length of a shortest pit in each of “Pit group B”through “Pit group D” is 0.112 μm (with the duty of 50%).

“Pit group B”, “Pit group C”, and “Pit group D” are different in pitlength and space length (i.e., duties of pit and space), and the pitlengths (duty of pits) decrease in this order. The duties of pits in therespective optical information recording mediums are as follows:

-   -   “Pit group B” . . . 51.7% (duty of spaces is 48.3%)    -   “Pit group C” . . . 50.3% (duty of spaces is 49.7%)    -   “Pit group D” . . . 48.8% (duty of spaces is 51.2%)

Moreover, each of the optical information recording mediums isconfigured by sequentially laminating, on a substrate, (i) a functionallayer which is made of tantalum and has a thickness of 12 nm and (ii) acover layer which is made up of a polycarbonate film and a transparentadhesive material and has a thickness of 100 μm. Further, in each of theoptical information recording mediums, information is recorded with the1-7 PP modulation recording method. That is, a length of a shortest pit(shortest space) is 2T, and a length of a longest pit (longest space) is8T.

In order for the reproduction device to stably carry out focus control,it is necessary to form the longest pit and the longest space so that areflectance in each of the optical information recording mediums fallswithin a predetermined range in which the focus control can be carriedout. The predetermined range can be considered as a tolerance ofreflectance which is (i) obtained from each of the optical informationrecording mediums and (ii) dealt with by the reproduction device as anidentical reflectance. In a case of the super-resolution medium 1 ofEmbodiment 1, it is possible to rephrase the predetermined range as apredetermined error range which encompasses both the reflectanceobtained from the data region 2 and the reflectance obtained from themedium information region 3. Further, it is possible to consider thattwo reflectances are substantially identical with each other, providedthat the two reflectances fall within the predetermined range.

The predetermined range is preferably within approximately ±5% relativeto a predetermined criterion, by taking into consideration factors suchas (1) deformation of the substrate caused during manufacturing, (2)film thickness distribution in the substrate, the information recordinglayer made up of the functional layer and the reflection film, or thecover layer, (3) unevenness in manufacturing of a light source, adetecting device (detector), and the like included in the reproductiondevice, and (4) measurement errors between the optical informationrecording mediums in focusing.

As above described, the longest space in the non-super-resolution mediumis larger than the irradiation region formed by reproduction light onthe non-super-resolution medium. From this, the predetermined criterionis preferably a reflectance obtained by irradiating the longest space ofthe non-super-resolution medium. That is, in a case where thesuper-resolution region (data region 2) and the non-super-resolutionregion (medium information region 3) are provided as in thesuper-resolution medium 1, a reflectance to be measured is preferablywithin approximately ±5% relative to a criterion which is a reflectanceof the non-super-resolution region.

In this Experiment Example, as illustrated in FIG. 10, the predeterminedrange (tolerance of reflectance) is set to 10.03% or higher and 11.12%or lower, on the basis of the predetermined criterion which is areflectance (10.56%) of the “Pit group A”.

As illustrated in FIG. 10, reflectances of “Pit group B”, “Pit group C”,and “Pit group D” are “9.51%”, “10.27%”, and “10.52%”, respectively, asa result of measurement. Moreover, the reflectances of “Pit group C” and“Pit group D” are merely slightly different from the reflectance of “Pitgroup A”, and fall within the predetermined range.

From the measurement results, it can be seen that the duty of spacesbecomes larger (i.e., length of space becomes longer) as the duty ofpits becomes smaller (i.e., length of pit becomes shorter), andaccordingly the reflectance obtained by irradiating the longest space(space of 8T) increases. Moreover, the reflectances of respective of“Pit group C” and “Pit group D” fall within the predetermined range, andit is therefore possible to consider that these reflectances and thereflectance of “Pit group A” can be dealt with by the reproductiondevice as identical reflectances.

Therefore, in the super-resolution medium 1, as the lengths of pits P1in the data region 2 which is the super-resolution region are set to beshorter, the reflectance obtained from the data region 2 is more likelyto be dealt with by the reproduction device as being identical with thereflectance obtained from the medium information region 3 which is thenon-super-resolution region. That is, even in sequential reproductionacross the data region 2 and the medium information region 3 which aredifferent in information recording density, it is possible to stablyreproduce information without causing, in information reproduction, atrouble such as being out-of-focus caused due to difference inreflectance.

Next, FIG. 11 shows results of measuring i-MLSE (Integrated-MaximumLikelihood Sequence Error Estimation) indicative of reproduction signalquality of optical information recording mediums “Pit group B”, “Pitgroup C”, and “Pit group D”.

In order to inhibit an error in reproduction and to quickly reproduceinformation, it is necessary to obtain good reproduction signal qualityand, in general, a value of i-MLSE needs to be 15.5% or lower.

As illustrated in FIG. 11, the values of i-MLSE of “Pit group B”, “Pitgroup C”, and “Pit group D” are “10.0%”, “10.5%”, and “15.2%”,respectively. From these measurement results, it can be seen that goodreproduction of information can be carried out even in a case where theshapes of the pits P1 in the super-resolution medium 1 are changed sothat the duty of the pits P1 becomes different from the duty of pits inthe general super-resolution medium. That is, it can be seen that thereproduction signal quality of the general super-resolution medium ismaintained also in the super-resolution medium 1.

Moreover, from the measurement results of FIG. 10 and FIG. 11, it can beseen that “Pit group C” and “Pit group D” are preferably applied to thedata region 2 of the super-resolution medium 1. That is, it can be seenthat, in a case where the 1-7 PP modulation recording method is employedand even in a case where the duty of the pits P1 is larger than the dutyof the spaces in the data region 2, it is sufficient that the duty ofthe pits P1 is smaller than the duty of the pits in the generalsuper-resolution medium (the duty of the pits in the generalsuper-resolution medium is not necessarily 50%). From this, according tothe super-resolution medium 1 having the data region 2 and the mediuminformation region 3 which are different in information recordingdensity, it is possible to cause the reproduction device to deal withthe reflectance obtained from the data region 2 as being identical withthe reflectance obtained from the medium information region 3, and it isalso possible to properly reproduce information by the reproductiondevice.

Embodiment 2

The following description will discuss another embodiment of the presentinvention with reference to FIGS. 12 and 13. For convenience ofexplanation, identical reference numerals are given to members havingfunctions identical to those described in Embodiment 1, and descriptionsof such members are omitted in Embodiment 2.

A super-resolution medium 1 of Embodiment 2 is different from that ofEmbodiment 1 in that lengths of pits P1 and spaces S1 in Embodiment 2are shorter than those of corresponding pits P1 and spaces S1 inEmbodiment 1. The other configurations (e.g., pit shapes in the mediuminformation region 3, and the like) are identical with those inEmbodiment 1.

In this case, a length of a longest space S1max is shorter than adiameter of an irradiation region formed by reproduction light L on thesuper-resolution medium 1. Therefore, in a case where the longest spaceS1max is irradiated with the reproduction light L, pits P1 which arepresent around the longest space S1max are also partially irradiated,and an obtained reflectance is decreased by a degree that corresponds toan amount of the reproduction light L with which the pits P1 arepartially irradiated.

However, even in this case, it is sufficient to form the pits P1 so thata reflectance obtained from the longest space S1max can be dealt with bythe reproduction device as being identical with a reflectance that isobtained from a longest space S2max (see (a) of FIG. 6). From this, evenin a case where the length of the longest space S1max is shorter thanthe diameter of the irradiation region formed by the reproduction lightL, it is possible to reproduce information without causing out-of-focusduring the sequential reproduction.

Example

Next, the following description will discuss an Example of thesuper-resolution medium 1 of Embodiment 2, with reference to FIG. 12.(a) of FIG. 12 illustrates a state in which a data region 2 is partially(in the vicinity of a longest space S1max) irradiated with reproductionlight L in the Example of the super-resolution medium 1 of Embodiment 2.

Note that a state in which the medium information region 3 in thesuper-resolution medium 1 of Embodiment 2 is irradiated withreproduction light L is identical with that illustrated in (a) of FIG.6. Moreover, configurations other than those described below areidentical with the configurations of the Example in Embodiment 1.Therefore, such configurations will not be repeatedly described indetail.

In this Example, as illustrated in (a) of FIG. 12, the data region 2includes a longest pit P1max (pit of 8T) whose length is 0.339 μm and alongest space S1max (space of 8T) whose length is 0.413 μm. That is, aduty of the pits P1 is approximately 45%, and a duty of the spaces S1 isapproximately 55%, and a shortest pit P1min (pit of 2T, not illustrated)in the data region 2 has a length of approximately 0.085 μm (≈0.094μm×2×0.45).

Note that the length of 0.094 μm is a length of a shortest pit P101minin a data region 102 in Comparative Example which will be describedlater. That is, the data region 2 in this Example is obtained bychanging, as above described, the duty in the data region 102 ofComparative Example.

In the data region 2 of this Example, a track pitch TpD is 0.32 μm, anda storage capacity is 40 GB (which corresponds to a storage capacityobtained in a case where the super-resolution medium 1 is a disk havinga diameter of 120 mm). That is, as compared with Example of Embodiment1, the lengths of the pits P1 and the lengths of the spaces S1 areshorter, and therefore the storage capacity is increased. Moreover, thelength of the longest space S1max is shorter than the diameter of theirradiation region formed by the reproduction light L.

Comparative Example

(b) of FIG. 12 illustrates a state in which a data region 102 ispartially (in the vicinity of a longest space S101max) irradiated withreproduction light L in a super-resolution medium 101 which isComparative Example of the super-resolution medium 1 of Embodiment 2.

Note that a state in which the medium information region 103 inComparative Example is irradiated with reproduction light L is identicalwith that illustrated in (a) of FIG. 6. Moreover, configurations otherthan those described below are identical with the configurations of theComparative Example in Embodiment 1. Therefore, such configurations willnot be repeatedly described in detail.

In the super-resolution medium 101 of Comparative Example of Embodiment2, a length of a shortest pit P101min (pit of 2T, not illustrated) inthe data region 2 is 0.094 μm, and a track pitch TpD in the data region2 is 0.32 μm.

As illustrated in (b) of FIG. 12, in the data region 102, a length of alongest pit P1max (pit of 8T) and a length of a longest space S1max(space of 8T) are both 0.376 μm. That is, a duty of the pits P101 and aduty of the spaces S101 are both 50%. Note that the data region 2 has astorage capacity of 40 GB (which corresponds to a storage capacityobtained in a case where the super-resolution medium 101 is a diskhaving a diameter of 120 mm).

[Comparison with Comparative Example]

As illustrated in (a) and (b) of FIG. 12, pits P1 are partiallyirradiated with the reproduction light L with which the space S1max isirradiated in Example, and pits P101 are partially irradiated with thereproduction light L with which the space S101max is irradiated inComparative Example. Therefore, a reflectance obtained by thereproduction device is decreased by a degree that corresponds to anamount of the reproduction light L with which the pits P1 or P101 areirradiated.

On the other hand, a size of the pit P1 in Example is smaller than thatof the pit P101 which (i) is of Comparative Example and (ii) correspondsto the pit P1. That is, the duty of the pits P1 in Example is smallerthan the duty of the pits P101 in Comparative Example. Therefore, aratio of a part of the pits P1 which part accounts for the irradiationregion formed by the reproduction light L in Example is smaller than aratio of a part of the pits P101 which part accounts for the irradiationregion formed by the reproduction light L in Comparative Example.

This makes it possible to enhance the reflectance obtained from thelongest space S1max in the data region 2 of Example, as compared withComparative Example. Further, in this Example, the reflectance obtainedfrom the longest space S1max in the data region 2 can be dealt with bythe reproduction device as being identical with the reflectance obtainedfrom the longest space S2max in the medium information region 3.

As such, according to the super-resolution medium 1, it is possible topromptly and surely reproduce, during the sequential reproduction,pieces of information which are recorded in separate regions, as withEmbodiment 1, even in a case where the length of the longest space S1maxis shorter than the diameter of the irradiation region formed by thereproduction light L.

Moreover, the pits P1 are smaller than those of Embodiment 1, and it istherefore possible to increase a storage capacity of the data region 2.

Experiment Example

Next, the following description will discuss an Experiment Examplerelating to the super-resolution medium 1 of Embodiment 2, withreference to FIG. 13. FIG. 13 illustrates results of experiment carriedout in an Experiment Example relating to the super-resolution medium 1.In this Experiment Example, appropriate lengths (duty) of the pits P1and the spaces S1 in the data region 2 are verified. Note, however, thatthe results of verification are merely an example, and a tolerancethereof can be changed in accordance with a reproduction status.

Note that an evaluation device used in this Experiment Example isidentical with the evaluation device used in Experiment Example ofEmbodiment 1. Moreover, optical information recording mediums “Pit groupE” through “Pit group G” have structures similar to those of the opticalinformation recording mediums “Pit group B” through “Pit group D”employed in Experiment Example of Embodiment 1, except for shapes ofpits. Therefore, such structures will not be repeatedly described indetail.

FIG. 13 shows results of measuring reflectances obtained from opticalinformation recording mediums “Pit group A” and “Pit group E” through“Pit group G” which are different in pit length. The measurement iscarried out with a BD standard evaluation device and a reproductionlight intensity is 1.0 mW in the measurement.

In FIG. 13, “Pit group E” through “Pit group G” are optical informationrecording mediums each including a super-resolution region which has atleast one pit whose length is shorter than that of an optical systemresolution limit. A length of a shortest pit in each of “Pit group E”through “Pit group G” is 0.094 μm (with the duty of 50%).

“Pit group E”, “Pit group F”, and “Pit group G” are different in pitlength and space length (i.e., duties of pit and space), and the pitlengths (duty of pits) decrease in this order. Moreover, in each of the“Pit group E” through “Pit group G”, in a case where a longest space isirradiated with reproduction light L, pits which are present around thelongest space are also partially irradiated with the reproduction lightL.

As illustrated in FIG. 13, reflectances of “Pit group E”, “Pit group F”,and “Pit group G” are “9.85%”, “10.37%”, and “10.40%”, respectively, asa result of measurement. Moreover, the reflectances of “Pit group F” and“Pit group G” are merely slightly different from the reflectance of “Pitgroup A”, and fall within the predetermined range.

From the measurement results, it can be seen that the duty of spacesbecomes larger as the duty of pits becomes smaller, and accordingly thereflectance obtained by irradiating the longest space (space of 8T)increases. Moreover, the reflectances of respective of “Pit group F” and“Pit group G” fall within the predetermined range, and it is thereforepossible to consider that these reflectances and the reflectance of “Pitgroup A” can be dealt with by the reproduction device as identicalreflectances.

Therefore, in the super-resolution medium 1, as the lengths of the pitsP1 in the data region 2 which is the super-resolution region are set tobe shorter, the reflectance obtained from the data region 2 are morelikely to be dealt with by the reproduction device as being identicalwith the reflectance obtained from the medium information region 3 whichis the non-super-resolution region.

Moreover, even in a case where a size of the pits P1 is made smallerthan that in Example of Embodiment 1 and consequently the pits P1 areirradiated with reproduction light L with which the longest space S2maxis irradiated, it is possible to deal with the reflectance by thereproduction device as above described, by setting the duty of the pitsP1 to be smaller. That is, it is possible to enlarge a storage capacityof the super-resolution medium 1.

Embodiment 3

The following description will discuss another embodiment of the presentinvention with reference to FIGS. 14 and 15. For convenience ofexplanation, identical reference numerals are given to members havingfunctions identical to those described in Embodiments 1 and 2, anddescriptions of such members are omitted in Embodiment 3.

FIG. 14 illustrates a polarity of pits P1 and P2. As illustrated in FIG.14, the super-resolution medium 1 of Embodiment 3 is different from thatof Embodiment 1 (in-pit form) in that pits P1 and P2 having a convexshape are formed on a substrate 4 (i.e., formed in an on-pit form). Theother configurations are identical with those of Embodiment 1.

Example

Next, the following description will discuss an Example of thesuper-resolution medium 1 of Embodiment 3, with reference to FIG. 15.FIG. 15 is a view illustrating an Example of the super-resolution medium1, where (a) illustrates a state in which a medium information region 3is partially (in the vicinity of a longest space S2max) irradiated withreproduction light L and (b) illustrates a state in which a data region2 is partially (in the vicinity of a longest space S1max) irradiatedwith reproduction light L.

The super-resolution medium 1 in this Example has configurations similarto those in the Example illustrated in FIG. 6, except that the pits P1and P2 have a convex shape. According to the arrangement, in a casewhere the longest space S2max in the medium information region 3 isirradiated with the reproduction light L, the pits P2 will not beirradiated with the reproduction light L (see (a) of FIG. 15). Moreover,in a case where the longest space S1max in the data region 2 isirradiated with the reproduction light L, the pits P1 will not beirradiated with the reproduction light L, unlike a generalsuper-resolution medium (see (b) of FIG. 15).

Therefore, according to the super-resolution medium 1 in which the pitsP1 and P2 have the convex shape, the reproduction device can deal with areflectance obtained from the longest space S1max in the data region 2as being identical with a reflectance obtained from the longest spaceS2max in the medium information region 3, as with Embodiment 1.

Embodiment 4

The following description will discuss yet another embodiment of thepresent invention, with reference to FIG. 16. For convenience ofexplanation, identical reference numerals are given to members havingfunctions identical to those described in Embodiments 1 through 3, anddescriptions of such members are omitted in Embodiment 4.

A super-resolution medium 1 of Embodiment 4 is different from that ofEmbodiment 2 in that a data region 2 in Embodiment 4 has a narrowertrack pitch TpD.

Example

Next, the following description discusses an Example of thesuper-resolution medium 1 of Embodiment 4, with reference to FIG. 16.FIG. 16 is a view illustrating a state in which the data region 2 ispartially (in the vicinity of a longest space S1max) irradiated withreproduction light L.

Note that a state in which a medium information region 3 in thesuper-resolution medium 1 of Embodiment 4 is irradiated withreproduction light L is identical with that illustrated in (a) of FIG.6. Moreover, configurations other than those described below areidentical with the configurations of the Example in Embodiment 2.Therefore, such configurations will not be repeatedly described indetail.

In the data region 2 of this Example, a longest pit P1max (pit of 8T)has a length of 0.301 μm and the longest space S1max (space of 8T) has alength of 0.451 μm (see FIG. 16). That is, a duty of pits P1 isapproximately 40% and a duty of spaces S1 is approximately 60%, and ashortest pit P1min (pit of 2T, not illustrated) in the data region 2 hasa length of approximately 0.075 μm (≈0.094 μm×2×0.40).

Note that, as described in the Example of Embodiment 2, the length of0.094 μm is the length of the shortest pit P101min in the data region102 of the Comparative Example in Embodiment 2. That is, the data region2 in this Example is obtained by changing the duty in the data region102 of the Comparative Example of Embodiment 2 as described above.

Further, in this Example, the track pitch TpD of the data region 2 is0.29 μm, and the data region 2 has a storage capacity of 44 GB (whichcorresponds to a storage capacity obtained in a case where thesuper-resolution medium 1 is a disk having a diameter of 120 mm).

That is, as compared with the Example of Embodiment 2, the lengths ofthe pits P1 and the lengths of the spaces S1 are shorter, and thereforethe storage capacity is further increased. Moreover, the length of thelongest space S1max is shorter than the diameter of the irradiationregion formed by the reproduction light L on the super-resolution medium1.

Comparative Example

A super-resolution medium 101 of a Comparative Example of this Exampleis identical in structure with that of the Comparative Example inEmbodiment 2, and therefore descriptions for the super-resolution medium101 are omitted here. Note that a state is illustrated in (b) of FIG. 12in which a data region 102 of the super-resolution medium 101 ispartially (in the vicinity of S101max) irradiated with reproductionlight L. Note that the track pitch of the data region 102 is 0.32 μm.

[Comparison with Comparative Example]

As with Embodiment 2, a size of the pit P1 in Example is smaller thanthat of the pit P101 which (i) is of Comparative Example and (ii)corresponds to the pit P1. Further, since the track pitch TpD is madenarrower in Example, pits P1 of adjacent tracks may also be irradiatedwith the reproduction light L with which the longest space S1max isirradiated. In this case, therefore, a reflectance may decrease. Inorder to avoid this, in this Example, the duty of the pits P1 is madefurther smaller than that of the Example in Embodiment 2.

This makes it possible to prevent the pits P1 of the adjacent tracksfrom being irradiated with the reproduction light L, and it is thereforepossible to eliminate influence, which occurs due to the shortening ofthe track pitch TpD, on a reflectance to be measured.

Further, as with Embodiment 2, even if the pits P1 which are on a trackon which the longest space S1max is provided are partially irradiatedwith the reproduction light L with which the longest space S1max isirradiated, the reflectance obtained from the data region 2 can be dealtwith by the reproduction device as being identical with the reflectanceobtained from the medium information region 3, because the irradiatedpart of the pits P1 can be made smaller than that in ComparativeExample.

As described above, the track pitch TpD and the sizes of the pits P1 inthe data region 2 of Example are smaller than the track pitch and thesizes of the pits P101 of Comparative Example, so that the number oftrack pitches and the number of pits become larger in Example ascompared with Comparative Example. This makes it possible to increase astorage capacity as compared with Comparative Example. Further, thetrack pitch TpD and the pits P1 in this Example are smaller than thosein the Example of Embodiment 2, and it is therefore possible to furtherincrease the storage capacity.

[Modification Examples of Super-Resolution Medium 1 of Embodiments 1Through 4]

A shape of the pits P1 is not limited to the one described above,provided that (1) it is possible to cause the production device to dealwith the reflectance obtained from the data region 2 as being identicalwith the reflectance obtained from the medium information region 3 and(2) it is possible to properly reproduce information by the reproductiondevice.

For example, it is possible that (i) only the duty of the longest pitP1max is smaller than that of a longest pit of a generalsuper-resolution medium and (ii) the duty of the other pits P1 isidentical with that of pits of the general super-resolution medium. Thatis, it is possible that only the duty of the longest space S1max isgreater than that of a longest space of the general super-resolutionmedium.

Generally, a shortest pit (shortest space) or a pit equivalent to theshortest pit (a space equivalent to the shortest space) accounts formost of influence on reproduction signal quality, and a longest pit or alongest space hardly exerts influence on the reproduction signalquality. Note that, in a case where the 1-7 PP modulation recordingmethod is employed, the shortest pit is a pit of 2T, a pit equivalent tothe shortest pit is a pit of 3T, the shortest space is a space of 2T,and a pit equivalent to the shortest space is a space of 3T.

Thus, by making only the duty of the longest pit or of the longest spacesmaller than that of the general super-resolution medium, it is possibleto further improve the reproduction signal quality, i.e., it is possibleto more properly reproduce information.

Further, it is possible that the pits P1 have (i) a width smaller thanthat of the pits of the general super-resolution medium and/or (ii) adepth shallower than that of the pits of the general super-resolutionmedium, while the duty of the pits P1 is identical with that of the pitsof the general super-resolution medium.

In a case where the duty of the pits P1 is identical with that of thepits of the general super-resolution medium, for example, pits P1 thatare present in the vicinity of the longest space S1max are alsopartially irradiated with the reproduction light L with which thelongest space S1max is irradiated.

However, in a case where the pits P1 have a small width, it is possibleto reduce a ratio of a part of the pits P1 which part accounts for theirradiation region formed by the reproduction light L, as compared witha case of the general super-resolution medium. In a case where the pitsP1 have a shallow depth, it is possible to approximate a reflectanceobtained from the part of the pits P1 to that obtained from the longestspace S1max, as compared with a case of the general super-resolutionmedium.

Therefore, in any of the above cases, it is possible to (i) approximatethe reflectance obtained from the data region 2 to a value of thereflectance obtained from the medium information region 3 and (ii) causethe reproduction device to deal with the reflectance obtained from thedata region 2 as being identical with the reflectance obtained from themedium information region 3.

That is, it is only necessary that a shape of the pits P1 is set so thata size of the longest space S1max, which size substantially determines areflectance in the data region 2, satisfies the above conditions (1) and(2).

Embodiment 5

The following description will discuss still another embodiment of thepresent invention with reference to FIGS. 17 through 19. For convenienceof explanation, identical reference numerals are given to members havingfunctions identical to those described in Embodiments 1 through 4, anddescriptions of such members are omitted in Embodiment 5.

<Configuration of Reproduction Device 10>

FIG. 17 schematically illustrates a configuration of a reproductiondevice 10 in accordance with Embodiment 5. The reproduction device 10 ofEmbodiment 5 is capable of reproducing both of (i) the super-resolutionmedium 1 in accordance with any one of Embodiments 1 through 4 and (ii)a normal medium.

As illustrated in FIG. 17, the reproduction device 10 includes a lasercontrol circuit 14, a signal processing circuit/control section 17(signal processing unit), a servo processing circuit 18 (servoprocessing unit), a spindle motor 19, an optical pickup 20 (reproductionlight irradiation unit), and a motor 21 for the optical pickup 20. Theoptical pickup 20 irradiates the super-resolution medium 1 or the normalmedium with reproduction light, and includes a polarization beamsplitter 12, a laser light source 13, and a detecting device 15. Notethat an optical information recording medium 11 illustrated in FIG. 17can be the super-resolution medium 1 or the normal medium.

In the reproduction device 10, first, the optical information recordingmedium 11 is rotated by the spindle motor 19, and the optical pickup 20is moved to a predetermined location by the motor 21. Then, in thereproduction device 10, an intensity of reproduction light, which is tobe emitted from the laser light source 13, is set to a predeterminedintensity, and the laser control circuit 14 causes the laser lightsource 13 to emit the reproduction light. This reproduction lightreaches the optical information recording medium 11 via the polarizationbeam splitter 12, and then light reflected from the optical informationrecording medium 11 reaches the detecting device 15 via the polarizationbeam splitter 12.

Based on the reflected light which has reached the detecting device 15,the detecting device 15 outputs an electric signal. This electric signalis supplied to the servo processing circuit 18, and the servo processingcircuit 18 carries out various servo controls (for example, a focusingservo and a tracking servo are controlled). The electric signal is alsosupplied to the signal processing circuit/control section 17. Based onthis electric signal, the signal processing circuit/control section 17(i) gives a driving instruction to the motor 21, or (ii) generatesreproduction data through decoding and supplies the reproduction data toan external device (e.g., a display device).

FIG. 18 illustrates a configuration of the signal processingcircuit/control section 17. The signal processing circuit/controlsection 17 decodes, by the PR(12221)ML method, a reproduction signalwaveform of, for example, reproduction data which has been obtained byirradiating the data region 2 with reproduction light emitted by theoptical pickup 20. As illustrated in FIG. 18, the signal processingcircuit/control section 17 includes a signal processing section 22, amedium identifying section 23, and an access location control section24.

The signal processing section 22 processes an electric signal which isindicative of medium identification information and has been suppliedfrom the optical pickup 20, and supplies the electric signal thusprocessed to the medium identifying section 23. Based on the electricsignal which is indicative of the medium identification information andhas been supplied from the signal processing section 22, the mediumidentifying section 23 identifies the optical information recordingmedium 11. Further, the medium identifying section 23 decodes, as thereproduction data, an electric signal which is indicative of a contentand has been supplied from the optical pickup 20, and outputs thereproduction data to the external device.

The access location control section 24 controls the motor 21 so that theoptical pickup 20 accesses an intended location of the opticalinformation recording medium 11. Note that, in a case where the dataregion 2 and the medium information region 3 are different in trackpitch in the super-resolution medium 1, it is preferable that the accesslocation control section 24 control the access location based on aresult of the identification of the optical information storage medium11 carried out by the medium identifying section 23.

The following description will discuss how the servo processing circuit18 operates the tracking servo. For example, there has been a trackingservo operating method in which a detector which is of the detectingdevice 15 and receives reflected light is divided into at least twosections, and a phase difference which occurs between detection signalsfrom the sections of the detector is utilized. In this operating method,however, tracking may become unstable in a region (data region 2) withhigh recording density, e.g., in a region whose storage capacitycorresponds to 45 GB or more in a disk having a diameter of 120 mm, andthus there is a possibility that sequential reproduction from the mediuminformation region 3 to the data region 2 cannot be carried out. Fromthis, in the data region 2, it is necessary to change the tracking servooperating method.

On the other hand, in a three-beam method, the PP method, the DPPmethod, or the like, a sufficient tracking error signal can be obtainedeven in a region having high recording density, and it is thereforepossible to stably carry out tracking. By employing, in the servoprocessing circuit 18, a tracking servo operating method (e.g., thethree-beam method, the PP method, or the DPP method) in which both ofthe data region 2 and the medium information region 3 can be tracked, itis possible to promptly, surely, and sequentially reproduce pieces ofinformation recorded in the two regions which are different in recordingdensity, even in a case, as in the super-resolution medium 1, whererecording density of one of regions is higher than that of the other ofthe regions.

Further, it is preferable that the signal processing circuit/controlsection 17 include a reproduction clock control section or areproduction speed control section (both are not illustrated).

In a case where the signal processing circuit/control section 17includes the reproduction clock control section, the reproduction clockcontrol section (i) keeps a reproduction clock which is used in thesignal processing section 22 unchanged (i.e., maintains a reproductionclock suitable for the normal medium) or (ii) switches the reproductionclock to a reproduction clock suitable for the super-resolution medium1, depending on the result of the identification of the opticalinformation recording medium 11 carried out by the medium identifyingsection 23. In a case where the signal processing circuit/controlsection 17 includes the reproduction speed control section, thereproduction speed control section (i) keeps a reproduction speedunchanged (i.e., maintains a reproduction speed suitable for the normalmedium) by controlling the spindle motor 19, or (ii) switches thereproduction speed to a reproduction speed suitable for thesuper-resolution medium 1, depending on the result of the identificationof the optical information recording medium 11 carried out by the mediumidentifying section 23.

The above description has dealt with the process example in which themedium identification information of the optical information recordingmedium 11 contains reproduction speed information. Note, however, thatthe reproduction speed information is not always contained in the mediumidentification information. In a case where the reproduction speedinformation is not contained in the medium identification information,the signal processing circuit/control section 17 is configured toinclude a reproduction speed information obtaining section (reproductionspeed information obtaining unit) (not illustrated). By causing thereproduction speed information obtained by the reproduction speedinformation obtaining section to be outputted to the reproduction clockcontrol section or to the reproduction speed control section, it ispossible to achieve a reproduction clock and a reproduction speed thatare suitable for the optical information recording medium 11 insertedinto the reproduction device 10, even in a case where the mediumidentifying section 23 is not provided.

Furthermore, it is preferable that the signal processing circuit/controlsection 17 include a power control section (not illustrated).

In a case where the signal processing circuit/control section 17includes the power control section, the power control section (i) keepsan intensity of reproduction light which is to be emitted from the laserlight source 13 unchanged (i.e., maintains a reproduction lightintensity suitable for the normal medium) or (ii) switches, bycontrolling the laser control circuit 14, the intensity of reproductionlight to an intensity which is suitable for the super-resolution medium1, depending on the result of the identification of the opticalinformation recording medium 11 carried out by the medium identifyingsection 23.

The above description has dealt with the process example in which themedium identification information of the optical information recordingmedium 11 contains reproduction light intensity information. Note,however, that the reproduction light intensity information is not alwayscontained in the medium identification information. In a case where thereproduction light intensity information is not contained in the mediumidentification information, the signal processing circuit/controlsection 17 is configured to include a reproduction light intensityinformation obtaining section (reproduction light intensity informationobtaining unit) (not illustrated). By causing the reproduction lightintensity information obtained by the reproduction light intensityinformation obtaining section to be outputted to the power controlsection, it is possible to achieve emission of reproduction light at anintensity that is suitable for the optical information recording medium11 inserted into the reproduction device 10, even in a case the mediumidentifying section 23 is not provided.

Furthermore, it is preferable that the signal processing circuit/controlsection 17 include a polarity identifying section (polarity identifyingunit) (not illustrated).

In a case where the signal processing circuit/control section 17includes the polarity identifying section, the signal processing section22 processes an electric signal (polarity identifying signal) indicativeof polarity information supplied from the optical pickup 20, andsupplies the electric signal thus processed to the polarity identifyingsection. Based on the polarity identifying signal supplied from thesignal processing section 22, the polarity identifying sectionidentifies a polarity of pits of the optical information recordingmedium 11. The servo processing section 18 then operates a trackingservo based on the result of identifying, by the polarity identifyingsection, the polarity of the pits of the optical information recordingmedium 11.

Furthermore, it is preferable that the signal processing circuit/controlsection 17 include a region location information recognition section(region location information recognition unit) and an informationreproduction condition control section (information reproductioncondition control unit).

In a case where the signal processing circuit/control section 17includes the region location information recognition section and theinformation reproduction condition control section, the signalprocessing section 22 processes an electric signal (data region locationsignal) which is indicative of data region location information and hasbeen supplied from the optical pickup 20, and supplies the electricsignal thus processed to the region location information recognitionsection. Based on the data region location signal supplied from thesignal processing section 22, the region location informationrecognition section recognizes a location of a data region in theoptical information recording medium 11. Based on the location of thedata region which location has been recognized by the region locationinformation recognition section, the information reproduction conditioncontrol section switches the information reproduction condition to aninformation reproduction condition suitable for the data region. Thatis, by controlling the laser control circuit 14 and/or the spindle motor19, the information reproduction condition control section switches thereproduction light intensity and/or the reproduction speed to areproduction light intensity and/or a reproduction speed suitable forthe super-resolution medium 1.

<Operational Processes of Reproduction Device 10>

The following description will discuss operational processes of thereproduction device 10.

When the optical information recording medium 11 has been inserted inthe reproduction device 10, the access location control section 24 ofthe signal process circuit/control section 17 controls the motor 21 forthe optical pickup 20 so that a medium information region which is aninitial access location for reproducing the optical informationrecording medium 11 is irradiated with reproduction light which isemitted by the laser light source 13 at a reproduction light intensitythat (i) is for the normal medium and (ii) is predetermined for aninitial stage of reproduction. Then, the medium identificationinformation (i) that is recorded in the medium information region and(ii) that indicates whether the optical information recording medium 11is the super-resolution medium or the normal medium, i.e., whether ornot a data region of the optical information recording medium 11 is in asuper-resolution form, is processed by the signal processing section 22of the signal processing circuit/control section 17 via the detectingdevice 15, and the optical information recording medium 11 is thenidentified by the medium identifying section 23.

After that, the data region 2 is accessed, and a content recorded in thedata region 2 is reproduced as reproduction data through the detectingdevice 15 and the signal processing section 22.

The following description will discuss how the signal processing section22 carries out decoding. In the BDs in which information is recorded bythe 1-7 PP modulation recording method at a density higher than that ofCDs and/or DVDs, the partial response maximum likelihood (PRML) decodingis used. Examples of the PRML encompass the PR(12221)ML that is used inBDXL™.

In a case where a modulation recording method by which information isrecorded in the data region 2 is, for example, the modified frequencymodulation (MFM) recording method, information is recorded by use ofpits and spaces of 1T, 1.5T, and 2T, and this restricts a degree offreedom in shape of pits P1 that is selectable to make the data region 2have a reflectance that is substantially identical with that of themedium information region 3. For this reason, there is a possibilitythat proper reproduction signal quality cannot be maintained. However,in a case of an optical information recording medium in whichinformation is recorded by the 1-7 PP modulation recording method,information is recorded by use of pits and spaces of from 2T to 8T.Further, a reflected light amount is defined by mainly a length of thespace of 8T which hardly exerts influence on reproduction signalquality. Therefore, in a case where the 1-7 PP modulation recordingmethod is employed to record information in the super-resolution medium1, it is possible to enhance the degree of freedom in selectable shapeof the pits P1, and this makes it possible to produce thesuper-resolution medium 1 with ease.

In addition, in Embodiment 5, the PR(12221)ML method is employed as adecoding method of the signal processing section 22. That is, in thereproduction method of Embodiment 5, a reproduction signal waveform ofreproduction data, etc. that has been obtained by irradiating the dataregion 2 with reproduction light is decoded by the PR(12221)ML method.This allows the reproduction device 10 to handle the super-resolutionmedium 1 which has a high degree of freedom in selectable shape of thepits P1, and it is possible to reproduce information with highreliability while maintaining proper reproduction signal quality.

Note that the decoding method of the signal processing section 22 is notlimited to the PR(12221)ML method, and may be a binary detection method,a PR(1221)ML method, or the like, provided that such a decoding methodmakes it possible to decode information which has been recorded in thesuper-resolution medium 1 by a given modulation method.

(Another Example of Operational Processes of Reproduction Device 10)

The following description will discuss another example of operationalprocesses that the reproduction device 10 carries out in a case wherethe signal processing circuit/control section 17 includes (i) thereproduction clock control section, (ii) the power control section,(iii) the polarity identifying section, (iv) the region locationinformation recognition section, and (v) the information reproductioncondition control section. The following description will mainly discusshow the operational processes of this example are different from thoseof the reproduction device 10 described above.

The medium identifying section 23 first identifies the opticalinformation recording medium 11. In a case where a result of theidentification indicates that the optical information recording medium11 is a normal medium, an intensity of and a reproduction clock ofreproduction light are kept unchanged, and a data region of the normalmedium is accessed. In a case where the result of the identificationcarried out by the medium identifying section 23 indicates that theoptical information recording medium 11 is the super-resolution medium1, the power control section can control the laser control circuit 14based on the identification result so that the reproduction light isadjusted to have a predetermined intensity suitable for thesuper-resolution medium 1. Concurrently with this adjustment, thereproduction clock control section can change, based on theidentification result, the reproduction clock to a predeterminedreproduction clock for the super-resolution medium 1.

Further, in a case where at least the PP method, the DPP method, or thelike is used as a tracking servo operating method, pit polarityinformation is reproduced (i) which is recorded in the mediuminformation region 3 of the super-resolution medium 1 and (ii) whichindicates whether the pits P1 and P2 are in the in-pit form or in theon-pit form. A pit polarity signal indicative of the pit polarityinformation is supplied to the signal processing section 22 via thedetecting device 15, and is then processed by the signal processingsection 22. After that, the polarity identifying section identifies apolarity of the pits P1 and P2. Based on a result of identifying thepolarity of the pits P1 and P2 by the polarity identifying section, theservo processing circuit 18 selects a servo-process that is suitable forthe tracking servo for the super-resolution medium 1.

Subsequently, the data region location information is reproduced (i)which is recorded in the medium information region 3 and (ii) whichindicates a location of the data region 2. A data region location signalindicative of the data region location information is supplied to thesignal processing section 22 via the detecting device 15, and is thenprocessed by the signal processing section 22. After that, the regionlocation information recognition section recognizes the location of thedata region 2.

Subsequently, the data region 2 is accessed at a reproduction lightintensity for the super-resolution medium 1 and, based on the locationof the data region 2 which location has been recognized by the regionlocation information recognition section, the information reproductioncondition control section switches the information reproductioncondition to an information reproduction condition suitable for the dataregion 2. That is, by controlling the laser control circuit 14 and/orthe spindle motor 19, the information reproduction condition controlsection switches the reproduction light intensity and/or thereproduction speed to a reproduction light intensity and/or areproduction speed suitable for the data region 2. As such, a contentrecorded in the data region 2 is reproduced as reproduction data throughthe detecting device 15 and the signal processing section 22.

The above description has dealt with the processes to be carried out ina case where the medium identification information of the opticalinformation recording medium 11 contains the reproduction speedinformation and the reproduction light intensity information. Note,however, that the reproduction speed information is not always containedin the medium identification information. In a case where thereproduction speed information is not contained in the mediumidentification information, the signal processing circuit/controlsection 17 includes the reproduction speed information obtainingsection. In a case where the optical information recording medium 11 hasbeen identified as the super-resolution medium 1 as a result of theidentification carried out by the medium identifying section 23, areproduction signal indicative of the reproduction speed information issupplied from the reproduction speed information obtaining section tothe reproduction clock control section or to the reproduction speedcontrol section via the detecting device 15 and the signal processingsection 22 so that, based on the reproduction signal, the reproductionclock is changed to a predetermined reproduction clock for thesuper-resolution medium 1.

Further, the reproduction light intensity information is not alwayscontained in the medium identification information. In a case where thereproduction light intensity information is not contained in the mediumidentification information, the signal processing circuit/controlsection 17 includes the reproduction light intensity obtaining section.In a case where the optical information recording medium 11 has beenidentified as the super-resolution medium 1 as a result of theidentification carried out by the medium identifying section 23, areproduction signal indicative of the reproduction light intensityinformation is supplied from the reproduction light intensityinformation obtaining section to the power control section via thedetecting device 15 and the signal processing section 22 so that thelaser control circuit 14 is controlled to adjust, based on thereproduction signal, the reproduction light intensity to be apredetermined reproduction light intensity suitable for thesuper-resolution medium 1.

As such, since the super-resolution medium 1 is configured as describedabove, the reproduction device 10 can easily and accurately identify, ata low reproduction light intensity for the normal medium, whether or notan inserted optical information recording medium is the super-resolutionmedium 1. The reproduction device 10 can thus reproduce both of thesuper-resolution medium 1 and the normal medium. Further, since theidentification can be carried out at the low reproduction lightintensity for the normal medium, (i) it is possible to reduce electricpower consumed by the reproduction device 10 and (ii) the normal mediumwill not be broken due to the reproduction light intensity for thesuper-resolution medium 1.

In a case where the reproduction device 10 reproduces pieces ofinformation recorded in the super-resolution medium 1, the reproductiondevice 10 can deal with the reflectance obtained from the data region 2as being identical with the reflectance obtained from the mediuminformation region 3. Therefore, during the sequential reproduction, thereproduction device 10 can reproduce information from a second one ofregions without repeatedly carrying out a control that (i) is includedin reproduction controls for a first one of the regions and (ii) can bemaintained in the second one of the regions.

<Reasons for Carrying Out Above Processes>

(Reason for Switching Reproduction Clock)

The following description will discuss, with reference to (a) and (b) ofFIG. 19, the reason why it is preferable that the reproduction device 1switch reproduction clocks between the super-resolution medium 1 and thenormal medium. In the descriptions below, examples are described (i) inwhich a read-only normal medium is reproduced at a reproduction clockfor the normal medium and (ii) in which the read-only normal medium isreproduced at a reproduction clock for the super-resolution medium 1.

Note that pieces of information are recorded in the normal medium by the1-7 PP modulation method. That is, based on a length T of a channel bit,pits having lengths of from a shortest pit of 2T to a longest pit of 8Tare provided on a substrate. Further, reproduction of the opticalinformation recording medium is carried out in the following manner.That is, (i) pits provided on the substrate are irradiated withreproduction light, (ii) an output signal obtained by the reflectedlight from the pits is sampled at the reproduction clock, and (iii) aresult of the sampling is decoded by PRML so that the output signal isreproduced. (a) of FIG. 19 illustrates a state in which the normalmedium is sampled at the reproduction clock for the normal medium and isthen decoded by PRML. In this state, the output signal corresponds topits illustrated on a lower side of (a) of FIG. 19. (b) of FIG. 19illustrates a state in which the normal medium is sampled at thereproduction clock for the super-resolution medium 1 and is then decodedby PRML. In this state, the output signal corresponds to pitsillustrated on a lower side of (b) of FIG. 19.

The following description will discuss a case where the normal medium isreproduced at the reproduction clock for the super-resolution medium 1.Note that the super-resolution medium 1 is twice a linear density of thenormal medium. From this, the reproduction clock for thesuper-resolution medium 1 has a width that is half of the reproductionclock for the normal medium.

In a case where the normal medium is reproduced at the reproductionclock for the super-resolution medium 1, a signal decoded by the PRMLindicates “1•1•1•1•0•0•0•0 1•1•1•1•1•1•1•1” (see (b) of FIG. 19).Therefore, in order to cause the decoded signal to be in a stateidentical with that of a case where the normal medium is reproduced asillustrated in (a) of FIG. 19, it is necessary to process (i) the signalof “1•1•1•1” as a pit of 2T and (ii) the signal of “1•1•1•1•1•1•1•1” asa pit of 4T, and this complicates the circuit. Therefore, in order tooptimally reproduce the normal medium and the super-resolution medium 1,it is preferable to change reproduction clocks between the normal mediumand the super-resolution medium 1. For the above reason, it ispreferable that the reproduction device 10 switch reproduction clocksbetween the super-resolution medium 1 and the normal medium.

Further, the reproduction clock switching information is recorded bypits P2 whose length is longer than that of the optical systemresolution limit of the reproduction device 10. Therefore, thesuper-resolution medium 1 can be reproduced at the reproduction clockfor the normal medium, and it is therefore unnecessary to carry outuseless switching of the reproduction clocks.

Further, in a case where reproduction clocks are switched between thenormal medium and the super-resolution medium 1, a circuit load of thereproduction device increases as follows, for example, two referenceoscillators are needed. In view of this, it is possible to switchreproduction speeds instead of the reproduction clocks.

For example, in a case where (i) the super-resolution medium 1 is twicethe linear density of the normal medium and (ii) the reproduction speedis switched to a half speed, signals to be reproduced are transferred atthe same speed as that used for the normal medium. In such a case, adecrease in reliability of reproduction as above described will notoccur even if the reproduction clocks are not switched. Therefore, it ispossible to employ the configuration in which the reproduction speedsare switched instead of the reproduction clocks.

Note that, in a case of the configuration in which the reproductionspeeds are switched, the circuit load can be reduced as compared withthe configuration in which the reproduction clocks are switched but atransfer rate of the super-resolution medium 1 is not different fromthat of the normal medium. In contrast, in a case of the configurationin which the reproduction clocks are switched, the transfer rate fortransferring information from the super-resolution medium 1 can beheightened.

(Reason for Switching Reproduction Light Intensity)

The following description will discuss the reason why it is preferablethat the reproduction device 10 switch a reproduction light intensitybetween the super-resolution medium 1 and the normal medium. In a casewhere super-resolution reproduction is enabled by heat, an excessivelylow reproduction light intensity causes insufficient heat andaccordingly the super-resolution reproduction cannot be carried out. Insuch a case, it is necessary to reproduce information recorded at leastin the data region 2 of the super-resolution medium 1 at a reproductionlight intensity higher than that for the normal medium. Meanwhile, it ispossible to avoid rapid deterioration of the normal medium byreproducing the normal medium at the reproduction light intensity forthe normal medium. Further, the reproduction light intensity informationis recorded by the pits P2 whose length is longer than that of theoptical system resolution limit of the reproduction device 10.Therefore, it is possible to reproduce the reproduction light intensityinformation of the super-resolution medium 1 at the reproduction lightintensity for the normal medium. It is therefore unnecessary to carryout useless switching of the reproduction clocks.

(Reason for Identifying Pit Polarity)

The following description will discuss the reason why it is preferablethat the reproduction device 10 identify a polarity of the pits P1 andP2. In a case where the reproduction device 10 operates a tracking servoby use of, for example, the PP method, the DPP method, or the like, apolarity (positive or negative) of a tracking error signal variesdepending on the polarity of the pits P1 and P2. From this, in a casewhere the polarity of the pits P1 and P2 is not to be identified, it isimpossible to immediately determine whether a tracking error signalwhich is in an on-track state is (i) at a center of amplitude of atracking error signal whose first derivation value relating to adistance from a center of the super-resolution medium 1 is positive or(ii) at a center of amplitude of a tracking error signal whose firstderivation value is negative. Therefore, in such a case, it is necessaryto check whether or not the irradiation location of reproduction lightis in the on-track state by checking, for example, whether or not areflected light amount varies due to the presence of the pits P1 and P2.

On the other hand, in a case where the reproduction device 10 identifiesthe polarity of the pits P1 and P2 based on the pit polarity informationrecorded in the super-resolution medium 1, it is possible to quicklyoperate the tracking servo with respect to the super-resolution medium1. Further, in such a case, it is possible to enhance a degree offreedom of methods for operating the tracking servo, and this makes iteasy to produce the reproduction device 10.

(Reason for Recognizing Location of Data Region 2)

The following description will discuss the reason why it is preferablethat the reproduction device 10 recognize the location of the dataregion 2. For example, in a case where (i) super-resolution reproductionis enabled by heat and, (ii) in order to reproduce information recordedin the medium information region 3 with good quality and to reduce aload applied to the optical pickup 20, reproduction speeds andreproduction light intensities for the data region 2 and for the mediuminformation region 3 are set to be identical with a maximum reproductionspeed and a minimum reproduction light intensity at each of which theinformation recorded in the medium information region 3 can bereproduced, heat that is needed for super-resolution reproductionbecomes insufficient in the data region 2 in which recording density ishigh, and it may therefore be impossible to carry out super-resolutionreproduction. In view of this, the reproduction speed is lowered or thereproduction light intensity is heighted when information recorded inthe data region 2 is reproduced, and it is thus possible to reproducethe information recorded in the data region 2 with good quality and toreduce the load applied to the optical pickup 20.

As such, in a case where the location of the data region 2 isrecognized, it is possible to switch the reproduction condition to areproduction condition in which the maximum reproduction speed and theminimum reproduction light intensity that are acceptable for the dataregion 2 and the medium information region 3 are taken intoconsideration. This makes it possible to (i) reproduce pieces ofinformation recorded in the data region 2 and the medium informationregion 3 with good quality and (ii) reduce the load applied to theoptical pickup 20.

[Example of Configuration Achieved by Software]

A control block of the reproduction device 10 (in particular, the signalprocessing circuit/control section 17) can be realized by a logiccircuit (hardware) provided in an integrated circuit (IC chip) or thelike or can be alternatively realized by software as executed by a CPU(Central Processing Unit).

In the latter case, the reproduction device 10 includes a CPU thatexecutes instructions of a program that is software realizing theforegoing functions; ROM (Read Only Memory) or a storage device (eachreferred to as “storage medium”) in which the program and various kindsof data are stored so as to be readable by a computer (or a CPU); andRAM (Random Access Memory) in which the program is loaded. An object ofthe present invention can be achieved by a computer (or a CPU) readingand executing the program stored in the storage medium. Examples of thestorage medium encompass “a non-transitory tangible medium” such as atape, a disk, a card, a semiconductor memory, and a programmable logiccircuit. The program can be supplied to the computer via anytransmission medium (such as a communication network or a broadcastwave) which allows the program to be transmitted. Note that the presentinvention can also be achieved in the form of a computer data signal inwhich the program is embodied via electronic transmission and which isembedded in a carrier wave.

[Main Points]

An optical information recording medium (super-resolution medium 1) inaccordance with an aspect 1 of the present invention includes: arecording layer which includes (i) a first region in which informationis recorded by a first pit row that includes a pit whose length isshorter than that of an optical system resolution limit of areproduction device and (ii) a second region in which information isrecorded by a second pit row that is made up of pits whose length isequal to or longer than that of the optical system resolution limit, ina case where (i) a reflectance calculated from a reflected light amountobtained from a longest pit or a longest space in the first pit row isdefined as a first reflectance and (ii) a reflectance calculated from areflected light amount obtained from a longest pit or a longest space inthe second pit row is defined as a second reflectance, the first pit rowbeing formed such that the first reflectance becomes substantiallyidentical with the second reflectance.

According to the configuration, information is recorded in the firstregion by the first pit row which includes the pit whose length isshorter than that of the optical system resolution limit of thereproduction device. Moreover, information is recorded in the secondregion by the second pit row which is made up of the pits whose lengthis equal to or longer than that of the optical system resolution limit.

In general, an information recording density in an optical informationrecording medium varies depending on a length of a shortest pit.Moreover, the pits forming the first pit row are different in lengthfrom the pits forming the second pit row. Therefore, an informationrecording density in the first region is different from that in thesecond region. In this case, there is a possibility that the firstreflectance and the second reflectance are different from each other soas to be assumed by the reproduction device as being not substantiallyidentical with each other, and the difference influences reproduction ofinformation.

In the optical information recording medium in accordance with theaspect of the present invention, the first pit row is formed such thatthe first reflectance becomes substantially identical with the secondreflectance.

This makes it possible to reduce a possibility that is caused becausethe first reflectance and the second reflectance are not substantiallyidentical with each other during sequential reproduction acrossdifferent regions. For example, it is possible to reduce a possibilitythat a size of an irradiation region changes which is formed byreproduction light on an optical information recording medium.Therefore, during the sequential reproduction, it is possible topromptly and surely reproduce information without repeatedly carryingout focus control.

That is, during the sequential reproduction, it is possible to reproduceinformation from a second one of regions without repeatedly carrying outa control that (i) is included in reproduction controls for a first oneof the regions and (ii) can be maintained in the second one of theregions. This makes it possible to improve information reproductionquality.

In the second region, the second pit row is formed which is made up ofthe pits whose length is equal to or longer than that of the opticalsystem resolution limit of the reproduction device. It is thereforepossible to reproduce information stored in the second region with areproduction light intensity that is suitable for reproducinginformation in a normal medium. Note that examples of the informationencompass various information (relating to the super-resolution medium)such as medium identification information, reproduction speedinformation, and a unique number of medium.

Note that the wording “the first reflectance becomes substantiallyidentical with the second reflectance” can be rephrased as follows: thatis, the first reflectance has a magnitude with which the reproductiondevice can deal with the first and second reflectances as beingidentical with each other, without providing different definitions ofreflectance in respective of the first region and the second region withrespect to the optical information recording medium (super-resolutionmedium 1) or the reproduction device.

In an aspect 2 of the present invention, the optical informationrecording medium is preferably arranged such that, in the aspect 1, in acase where (i) a first space which is longest among a plurality of firstspaces (space S1) that are formed between a plurality of pitsconstituting the first pit row is a longest first space (longest spaceS1max) and (ii) a second space which is longest among a plurality ofsecond spaces (space S2) that are formed between a plurality of pitsconstituting the second pit row is a longest second space (longest spaceS2max), the first pit row is formed such that a reflectance obtainedfrom the longest first space becomes substantially identical with areflectance obtained from the longest second space.

According to the configuration, the first pit row is formed in the firstregion such that a reflectance obtained from the longest first spacebecomes substantially identical with a reflectance obtained from thelongest second space. Therefore, during the sequential reproduction, itis possible to promptly and surely reproduce information.

In an aspect 3 of the present invention, the optical informationrecording medium is preferably arranged such that, in the aspect 2, alength of the longest first space is equal to or longer than a diameterof an irradiation region which is formed, on the optical informationrecording medium, by reproduction light emitted by the reproductiondevice.

According to the configuration, the length of the longest first space isequal to or longer than the diameter of the irradiation region which isformed by the reproduction light on the optical information recordingmedium. With the arrangement, in a case where the longest first space isirradiated with reproduction light, pits which constitute the first pitrow and exist on a track on which the longest first space exists willnot be irradiated with the reproduction light. Therefore, the firstreflectance becomes a reflectance that is derived only from the longestfirst space.

Meanwhile, in the second region, a length of the longest second space islonger than a diameter of an irradiation region formed by thereproduction light, and therefore the second reflectance becomes areflectance that is derived only from the longest second space.

From this, by forming the pits as above described, it is possible tocause the reproduction device to deal with the first reflectance asbeing substantially identical with the second reflectance.

An optical information recording medium in accordance with an aspect 4of the present invention is an optical information recording mediumwhich is to be reproduced by a reproduction device that (i) emitsreproduction light having a wavelength (λ) of 405 nm and (ii) includesan objective lens having a numerical aperture (NA) of 0.85, the opticalinformation recording medium including: a recording layer which includes(i) a first region in which information is recorded by a first pit rowthat includes a pit whose length is shorter than 119 nm and (ii) asecond region in which information is recorded by a second pit row thatis made up of pits whose length is equal to or longer than 119 nm, in acase where (i) a reflectance calculated from a reflected light amountobtained from a longest pit or a longest space in the first pit row isdefined as a first reflectance and (ii) a reflectance calculated from areflected light amount obtained from a longest pit or a longest space inthe second pit row is defined as a second reflectance, the first pit rowbeing formed such that the first reflectance becomes substantiallyidentical with the second reflectance.

According to the configuration, in addition to an effect brought aboutby the aspect 1, it is possible to carry out reproduction with asuper-resolution technique in the first region and to carry outreproduction with a non-super-resolution technique in the second regionby changing a reproduction light intensity or the like.

In an aspect 5 of the present invention, the optical informationrecording medium is preferably arranged, in any of the aspects 1 through4, such that the first pit row is formed by use of a 1-7 PP modulationrecording method.

According to the configuration, it is possible to enhance an informationrecording density, as compared with a case where information is recordedby use of pits having identical lengths. Moreover, it is possible toobtain good signal quality.

In an aspect 6 of the present invention, the optical informationrecording medium is preferably arranged, in any of the aspects 1 through5, such that the second region includes medium identificationinformation for specifying a type of a medium.

According to the configuration, it is possible to reproduce mediumidentification information with a reproduction light intensity that issuitable for reproducing information in a normal medium. Therefore, itis possible to identify that the optical information recording medium isa super-resolution medium, with use of the reproduction light intensitythat is suitable for reproducing information in the normal medium.

A reproduction method in accordance with an aspect 7 of the presentinvention is a method for reproducing an optical information recordingmedium of the aspect 5, the method preferably including the step of:decoding, with a PR(12221)ML method, a reproduction signal waveformwhich has been obtained by irradiating the first region withreproduction light.

According to the configuration, it is possible to (i) carry outreproduction that corresponds to an optical information recording mediumin which a degree of freedom in shape of pits forming the first pit rowin the first region is high, i.e., corresponds to an optical informationrecording medium which can be easily produced and (ii) reproduceinformation with high reliability while maintaining good reproductionsignal quality.

A reproduction device in accordance with an aspect 8 of the presentinvention is a reproduction device by which the optical informationrecording medium of the aspect 5 is reproducible, the reproductiondevice preferably including: a reproduction light irradiation unit forirradiating the optical information recording medium with reproductionlight; and a signal processing unit for decoding, with a PR(12221)MLmethod, a reproduction signal waveform which has been obtained byirradiating the first region with the reproduction light emitted by thereproduction light irradiation unit.

According to the configuration, (i) the reproduction device iscompatible with an optical information recording medium in which adegree of freedom in shape of pits forming the first pit row in thefirst region is high, i.e., compatible with an optical informationrecording medium which can be easily produced and (ii) reproduceinformation with high reliability while maintaining good reproductionsignal quality.

The present invention is not limited to the embodiments, but can bealtered by a skilled person in the art within the scope of the claims.An embodiment derived from a proper combination of technical means eachdisclosed in a different embodiment is also encompassed in the technicalscope of the present invention. Further, it is possible to form a newtechnical feature by combining the technical means disclosed in therespective embodiments.

INDUSTRIAL APPLICABILITY

The optical information recording medium (super-resolution medium) ofthe present invention is suitable for various optical disks such as anoptically-read disk, a magneto-optical disk, and a phase-change disk,and is also applicable to an information recording medium (such as amagnetic disk) which includes a recording mark whose length is shorterthan that of an optical system resolution limit. Moreover, thereproduction method and the reproduction device in accordance with thepresent invention can be applied to a method and a device forreproducing the optical information recording medium in accordance withthe present invention.

REFERENCE SIGNS LIST

-   1: Super-resolution medium (optical information recording medium)-   2: Data region (first region)-   3: Medium information region (second region)-   5: Functional layer-   10: Reproduction device-   17: Signal processing circuit/control section (signal processing    unit) 20: Optical pickup (reproduction light irradiation unit)-   P1: Pit (pits in first pit row)-   P2: Pit (pits in second pit row)-   P1max: Longest pit-   P2max: Longest pit-   S1max: Longest space-   S2max: Longest space-   L: Reproduction light-   λ: Wavelength-   NA: Numerical aperture

The invention claimed is:
 1. An optical information recording mediumcomprising: a recording layer which includes (i) a first region in whichinformation is recorded by a first pit row that includes a pit whoselength is shorter than that of an optical system resolution limit of areproduction device and (ii) a second region in which information isrecorded by a second pit row that is made up of pits whose length isequal to or longer than that of the optical system resolution limit, ina case where (i) a reflectance calculated from a reflected light amountobtained from a longest pit or a longest space in the first pit row isdefined as a first reflectance and (ii) a reflectance calculated from areflected light amount obtained from a longest pit or a longest space inthe second pit row is defined as a second reflectance, the first pit rowbeing formed such that the first reflectance becomes substantiallyidentical with the second reflectance, and the second region recordingtherein medium identification information for identifying a medium. 2.An optical information recording medium which is to be reproduced by areproduction device that (i) emits reproduction light having awavelength of 405 nm and (ii) includes an objective lens having anumerical aperture of 0.85, said optical information recording mediumcomprising: a recording layer which includes (i) a first region in whichinformation is recorded by a first pit row that includes a pit whoselength is shorter than 119 nm and (ii) a second region in whichinformation is recorded by a second pit row that is made up of pitswhose length is equal to or longer than 119 nm, in a case where (i) areflectance calculated from a reflected light amount obtained from alongest pit or a longest space in the first pit row is defined as afirst reflectance and (ii) a reflectance calculated from a reflectedlight amount obtained from a longest pit or a longest space in thesecond pit row is defined as a second reflectance, the first pit rowbeing formed such that the first reflectance becomes substantiallyidentical with the second reflectance, and the second region recordingtherein medium identification information for identifying a medium.
 3. Amethod for reproducing an optical information recording medium recitedin claim 1, said method comprising the step of: determining areproduction condition based on the medium identification informationwhich has been obtained by irradiating the second region withreproduction light.
 4. A method for reproducing an optical informationrecording medium recited in claim 2, said method comprising the step of:determining a reproduction condition based on the medium identificationinformation which has been obtained by irradiating the second regionwith reproduction light.